QE 


UC-NRLF 


LABORATORY  EXERCISES 

IN  STRUCTURAL  AND  HISTORICAL 

GEOLOGY 

A  LABORATORY  MANUAL  BASED  ON  FOLIOS  OF  THE 

UNITED  STATES  GEOLOGICAL  SURVEY,  FOR 

USE  WITH  CLASSES  IN  STRUCTURAL 

AND  HISTORICAL  GEOLOGY 


BY 

ROLLIN  D,  SALISBURY 

THE   UNIVERSITY  OF  CHICAGO 

AND 

ARTHUR  C.  TROWB RIDGE 

THE   STATE  UNIVERSITY  OF  IOWA 


NEW  YORK 

HENRY  HOLT  AND  COMPANY 
1913 


OE4I 


COPYRIGHT,  1913 

BY 

HENRY  HOLT  AND  COMPANY 


THE     MAPLE«PHBS8«TO«K«PA 


PREFACE 

This  manual  is  the  third  of  a  series  of  outlines  for  labora- 
tory work  in  general  geology.  The  first  is  a  little  manual 
based  on  topographic  maps  of  the  United  States  Geological 
Survey,  designed  for  use  in  elementary  courses  in  physiog- 
raphy, and  the  second  is  a  similar  manual  for  use  in  more 
advanced  courses  in  physiographic  geology.  The  present 
outline  is  based  on  folios  of  the  United  States  Geological 
Survey,  and  is  intended  to  accompany  courses  in  historical 
and  structural  geology.  The  previously  published  manuals 
follow  the  general  order  of  Salisbury's  Physiography,  and 
Chamberlin  and  Salisbury's  Geology,  Vol.  I,  respectively. 
This  manual  may  be  used  to  good  purpose  with  Chamberlin 
and  Salisbury's  Earth  History,  Vols.  II  and  III,  but  can 
be  adapted  to  any  other  thorough-going  text  on  historical 
geology. 

In  presenting  this  manual  to  teachers,  the  authors  believe 
that  laboratory  work,  such  as  here  outlined,  has  the  same 
importance  for  students  of  geology,  that  the  more  familiar 
phases  of  laboratory  work  have  for  students  of  chemistry 
and  physics,  and  that  no  course  in  geology,  involving  such 
topics  as  structural  geology,  the  evolution  of  the  North 
American  Continent,  or  the  geologic  history  of  the  various 
provinces  of  the  United  States,  is  adequate  without  an  ac- 
companiment of  map  work.  They  also  believe  that  folios 
of  the  United  States  Geological  Survey  form  the  best  basis 
for  such  work.  At  the  date  of  writing,  one  hundred  and 

iii 

258012 


iv  PREFACE 

eighty-one  folios  have  been  published  by  the  Survey,  and 
many  of  them,  especially  the  more  recent  ones,  are  well 
adapted  to-  the  work  outlined  in  this  manual.  It  is  also 
important  that  these  folios  should  be  understood  and  used 
by  persons  other  than  students  in  schools,  for  they  are  serv- 
iceable to  miners,  engineers,  contractors,  travellers,  etc., 
when  once  understood  by  them. 

The  adaptation  of  these  outlines  to  fit  the  needs,  the  time, 
the  laboratory  facilities,  and  the  amount  of  laboratory 
assistance  avaijable,  must  be  left  to  the  individual  teacher; 
but  two  methods  of  presentation  which  have  been  used  suc- 
cessfully by  the  authors,  are  suggested:  (1)  After  the 
assignment  of  an  exercise  is  made,  the  folios  are  placed  where 
the  students  may  study  them  at  their  convenience.  The 
class  is  divided  into  sections  of  four,  and  an  hour  for  con- 
ference with  the  instructor,  subsequent  to  the  study  of  the  folios, 
is  named  for  each  section.  In  these  conferences,  the  topic  of 
the  exercise  is  discussed  informally,  the  folios  being  used  for 
demonstration.  Either  before  or  after  conference,  questions 
so  designated  are  answered  in  writing,  and  the  papers  given 
to  the  instructor  for  correction.  (2)  By  the  other  method, 
definite  laboratory  periods  are  assigned,  their  duration  and 
frequency  being  determined  by  the  time  and  general  plan  of 
the  course,  and  the  degree  of  preparation  of  the  students. 
In  this  case,  all  the  work  is  done  in  the  laboratory  in  the 
presence  of  the  instructor  or  his  assistants.  The  students 
work  individually  or  in  pairs,  and  receive  help  or  criticism 
from  the  instructor  on  demand.  The  second  method  is  the 
better  with  younger  students,  where  time,  laboratory  space, 
assistance,  and  supply  of  folios  are  sufficient. 

Where  the  program  is  flexible,  it  is  better  to  have  the 
laboratory  work  timed  to  fit  the  class-room  work,  rather  than 


PREFACE  v 

on  specified  days.  The  authors  hold  firmly  to  the  view 
that,  apart  from  developing  familiarity  with  very  useful 
publications,  the  only  functions  of  these  laboratory  exercises 
in  geology  are  (1)  to  illustrate  and  emphasize  the  topics  or 
principles  discussed  in  the  class-room,  or  (2)  to  introduce  new 
topics  or  principles. 

For  a  group  of  twenty-five  students  in  the  laboratory, 
three  or  four  copies  of  each  folio  assigned  are  sufficient. 


LABORATORY  EXERCISES  IN 

STRUCTURAL  AND 
HISTORICAL  GEOLOGY 


INTRODUCTION 

Topographic  maps  show  the  topographic  forms  resulting 
from  the  work  of  the  various  physiographic  agents,  such  as 
running  water,  wind,  ground  water,  glaciers,  etc.  From  the 
study  of  these  maps,  some  interpretation  of  the  various 
processes  involved  in  developing  topography  can  be  made 
with  confidence.  The  study  of  geologic  maps  may  carry  the 
student  further.  Such  maps  show  the  various  rock  forma- 
tions which  appear  at  the  surface,  and  the  structure  sections 
show  their  relations  to  each  other,  the  positions  of  the  beds 
if  the  rock  is  stratified,  the  thicknesses  of  the  formations,  and 
many  other  things  to  which  attention  is  called  in  the  exercises 
which  follow.  From  these  various  facts  about  the  rocks  of 
a  region,  not  only  can  the  topography  be  interpreted  more 
certainly  than  from  topographic  maps,  but  the  history  of  the 
region  antedating  the  development  of  the  present  surface 
can  be  worked  out.  The  principles  involved  and  their 
applications,  are  brought  out  in  some  detail  in  the  exercises 
which  follow. 

Though  the  adaptation  of  the  exercises  presented  in  the 
following  pages  must  be  left  to  the  individual  teacher,  the 
questions  of  each  exercise  are  arranged  for  two  somewhat 

1 


2          STRUCTURAL  AND  HISTORICAL  GEOLOGY 

distinct  groups  of  students,  the  one  more  advanced  or  pur- 
suing a  fuller  course,  and  the  other  less  advanced  or  pur- 
suing a  briefer  course.  To  be  more  specific,  students  of  the 
grade  of  college  seniors,  pursuing  a  course  of  about  120 
hours  in  historical  geology,  after  a  thorough  course  in 
physiography,  would  be  regarded  as  belonging  to  the  first 
group;  while  students  of  less  maturity,  pursuing  a  course  of 
60  to  90  hours,  would  belong  to  the  second  group.  As 
used  by  the  authors,  the  complete  outline  of  work  presented 
herewith  accompanies  a  course  which  covers  Vols.  II  and 
III  of  Chamberlin  and  Salisbury's  Geology.  Omitting  the 
questions  marked  **,  the  work  here  outlined  is  done  by 
somewhat  less  mature  students  in  connection  with  a  half- 
year  course  in  historical  geology,  based  on  the  historical 
part  of  Chamberlin  and  Salisbury's  College  Geology. 

Unless  otherwise  directed,  students  of  the  first  group 
study  all  questions,  and  answer  in  writing  those  marked  * 
and  **.  Students  in  the  more  elementary  or  briefer  courses 
omit  the  questions  marked  **,  and  answer  in  writing  those 
marked  *.  In  many  instances  questions  not  marked  for 
written  answers  lead  up  to  those  which  are  to  be  answered 
in  writing;  hence  all  questions  should  be  studied  in  order, 
and  studied  with  care.  Students  who  have  some  knowl- 
edge of  geologic  maps  at  the  outset,  may  not  need  the  simpler 
exercises  of  the  Introductory  Series.  Individual  questions 
may  seem  to  some  teachers  unnecessarily  simple,  and  their 
answers  too  obvious  to  need  attention  (e.g.,  Number  1, 
under  Exercise  II);  but  the  experience  of  the  authors  is 
that  some  such  questions  are  needed  by  the  average 
student  in  the  early  stages  of  his  work.  There  is,  however, 
no  object  in  dwelling  on  questions  or  ideas  which  are  well 
understood. 


STRUCTURAL  AND  HISTORICAL  GEOLOGY          3 

The  work  here  outlined  should  include  a  minimum  of 
writing,  but  it  should  be  done  with  great  care.  The  written 
answers  should  be  concise  and  to  the  point.  Many  of  them 
can  be  given  in  a  word  or  a  short  sentence;  but  in  some  cases, 
detailed  explanations  are  called  for.  After  his  corrected 
paper  is  returned,  each  student  should  review  the  exercise 
with  the  folios  before  him,  in  order  to  see  where  mistakes 
were  made. 

While  the  deductions  called  for  in  the  exercises  are  to  be 
drawn  chiefly  from  the  study  of  the  folios,  reference  should 
be  made  to  the  text-book  used  in  the  course,  whenever  it  will 
be  helpful. 

In  the  study  of  the  folios,  most  time  should  be  put  on  the 
"Areal  Geology"  or  "Historical  Geology"  maps;  but  the 
"Structure  Section"  and  "Illustrations"  sheets  may  be  used 
where  they  are  found  in  the  folios,  and  the  text  of  the  folios 
may  be  referred  to,  in  order  to  corroborate  conclusions. 
"Surficial  Geology"  sheets  should  be  given  especial  atten- 
tion in  Exercise  XIII. 

By  observing  the  location  in  the  United  States  of  each 
folio  studied,  a  good  idea  of  the  geologic  history  of  each  prov- 
ince of  the  country  can  be  obtained  during  the  progress  of 
the  work. 

Exercises  I-VI  should  precede  the  strictly  historical  part 
of  the  course,  or  accompany  its  very  early  stages.  The 
work  outlined  in  Exercise  VII  should  accompany,  or  follow 
immediately,  the  class-room  work  on  the  Pre-Cambrian, 
and  should  be  completed  before  work  on  the  Cambrian  is 
begun.  The  work  outlined  in  Exercise  VIII  should  accom- 
pany, or  follow  immediately  the  study  of  the  Cambrian 
period,  and  be  completed  before  the  later  Paleozoic  periods 
are  studied.  Exercise  IX  might  be  divided  into  several; 


4          STRUCTURAL  AND  HISTORICAL  GEOLOGY 

but  many  of  the  principles  involved  were  developed  in 
connection  with  Exercise  VIII,  and  the  authors  have  found 
that  this  Exercise  (IX)  may  well  stand  as  a  unit,  and  ac- 
company the  study  of  the  later  Paleozoic  Systems.  The 
assignment  of  this  exercise  is  made  about  the  time  the 
Devonian  is  completed,  and  is  finished  before  the  Mesozoic 
is  begun.  The  later  exercises  are  used  in  a  similar  way. 

It  is  the  authors'  experience  that  the  earnest  students  set  a 
high  value  on  this  work. 

EQUIPMENT 

Geologic  Folios1 

ALABAMA  CALIFORNIA 

Gadsden  Colfax 

Stevenson  Downieville 

Lassen  Peak 
ARIZONA  Mother  Lode 

Bisbee  Nevada  City 

Bradshaw  Mountains  Pyramid  Peak 

Clifton  Redding 

Globe  San  Luis 

Santa  Cruz 
ARKANSAS  Sonora 

Fayetteville  Truckee 

Winslow 

COLORADO 
CALIFORNIA  Elmoro 

Bidwell  Bar  Engineer  Mountain 

Big  Trees  Needle  Mountains 

1  These  folios  may  be  obtained  from  the  Director  of  the  United 
States  Geological  Survey,  Washington,  D.  C.,  for  25  cents  per 
copy. 


STRUCTURAL  AND  HISTORICAL  GEOLOGY 


COLORADO 
Ouray 
Rico 
Silverton 
Spanish  Peaks 
Telluride 
Tenmile  District 
Walsenburg 

DELAWARE 
Dover 

DISTRICT  OF 

COLUMBIA 

Washington 

GEORGIA 

Ringgold 

IDAHO 

Boise 


ILLINOIS 

Chicago 
Danville 

INDIANA 

Patoka 

KENTUCKY 

Estillville 

London 

Richmond 


MAINE 

Penbbscot  Bay 
Rockland 

MARYLAND 

Accident-Grantsville 

Choptank 

Nomini 

Patuxent 

Pawpaw-Hancock 

St.  Marys 

MASSACHUSETTS 
Holyoke 

MICHIGAN 
Ann  Arbor 
Menominee 

MISSOURI 
Joplin 

MONTANA 

Fort  Benton 
,  Little  Belt  Mountains 
Three  Forks 

NEW  JERSEY 

Franklin  Furnace 

Passaic 

Trenton 


6 


STRUCTURAL  AND  HISTORICAL  GEOLOGY 


NEW  YORK 

New  York  City 
Watkins  Glen-Catatonk 

NORTH  CAROLINA 

Asheville 
Cranberry 
Mount  Mitchell 
Pisgah 

NORTH  DAKOTA 

Bismarck 

Casselton-Fargo 

Jamestown-Tower 


PENNSYLVANIA 

Claysville 

Elders  Ridge 

Elkland-Tioga 

Foxburg-Clarion 

Gaines 

Latrobe 

Masontown-Uniontown 

Mercersburg-Cham- 

bersburg 
Philadelphia 
Sewickley 
Warren 
Waynesburg 


OKLAHOMA 

Coalgate 

Tahlequah 

Tishomingo 

OREGON 
Coos  Bay 
Port  Orford 
Roseburg 

PENNSYLVANIA 

Amity 

Beaver 

Brownsville-Connells- 

ville 
Burgettstown-Carnegie 


SOUTH  DAKOTA 

Aberdeen-Redfield 

Belle  Fourche 

Edgemont 

Elk  Point 

Oelrichs 

Olivet 

Parker 


TENNESSEE 
Briceville 
Greeneville 
Maynardville 
Pikeville 
Roan  Mountain 
Sewanee 


STRUCTURAL  AND  HISTORICAL  GEOLOGY 


TEXAS 
Austin 
El  Paso 
Nueces 
Uvalde, 


UTAH 

Tintic 

VIRGINIA 

Bristol 

Fredericksburg 

Harpers  Ferry 

Monterey 

Norfolk 

Pocahontas 

Tazewell 

WASHINGTON 

Ellensburg 

Snoqualmie 

Tacoma 


WEST  VIRGINIA 
Buckhannon 
Charleston 
Franklin 
Piedmont 

WISCONSIN 

Lancaster-Mineral 

Point 
Milwaukee 

WYOMING 
Absaroka 
Aladdin 

Bald  Mountain-Dayton 
Cloud  Peak-Fort 

McKinney 
Devils  Tower 
Laramie-Sherman 
Newcastle 
Sundance 


A.  INTRODUCTORY  SERIES 

Before  taking  up  the  interpretation  of  geologic  maps,  it  is 
necessary  to  have  a  clear  idea  of  their  make-up,  and  of  the 
meaning  of  the  conventional  signs  on  them.  The  geologic 
maps  published  by  the  U.  S.  Geological  Survey  are  the 
standard  maps  of  this  sort  for  the  United  States,  and  the 
folios  of  the  Survey  are  the  principal  basis  for  the  fol- 
lowing studies.  The  purpose  of  Exercise  I  is  merely  to  in- 
troduce the  beginner  to  geologic  maps. 

EXERCISE  I 

GENERAL  FEATURES  OF  GEOLOGIC  FOLIOS 
I.  ASSIGNMENT 

A.  Two  or  three  of  the  following  folios: 
Cranberry,  N.  C.  Penobscot  Bay,  Me. 
Engineer  Mountain,  Colo.  Port  Orford,  Ore. 
Mercersburg-Chambersburg,  Pa.  Roan  Mountain,  Tenn. 
Passaic,  N.  J.  Sewanee,  Tenn. 

B.  Chapters   on   Structural   Geology  in  some  standard 
text-book,  as  Chamberlin  and  Salisbury's  College  Geology, 
pp.  394-413,  or  Vol.  I,  Geologic  Processes,  pp.  486-525. 

C.  Description  of  Geologic  Maps: 

Pp.  2  and  3  of  the  cover  of  any  folio  of  the  U.  S. 

Geological  Survey. 

Professional  Paper  60,  U.  S.  Geol.  Surv.,  pp.  12-18, 
3 


STRUCTURAL  AND  HISTORICAL  GEOLOGY          9 

H.  OUTLINE  FOR  STUDY 

1.  Note  the  following  points  in  connection  with  the  folios 
assigned: 

a)  The  number  of  maps,  and  the  title  of  each. 

b)  What  facts  are  shown  on  the  Areal  Geology  Sheet 
(any  one)   and  how  are  they  shown?     A  thorough  under- 
standing of  this  sheet  is  necessary,  as  most  of  the  work  of 
this  outline   is  based  upon  similar  maps.     (Read  carefully 
pp.  2  and  3  of  the  cover  of  a  recent  folio,  and  pp.   12-18 
of  Professional  Paper  60.) 

c)  What  is  shown  on  the  Structure  Section  Sheet,  in 
addition  to  what  is  shown  on  the  Areal  Geology  Sheet  ? 

d)  Note  the  Illustration  Sheet  if  the  folio  in  hand 
contains  one. 

e)  Make  a  brief  outline  of  the  topics  considered  in  the 
descriptive  text.     (The  texts  of  the  folios  will  be  used  in  this 
course  chiefly  to  find  data  which  cannot  be  read  from  the 
maps  directly,  or  to  corroborate  conclusions  drawn  from  the 
study  of  the  maps.) 

2.  What  three  great  classes  of  rocks  are  shown  on  geologic 
maps  ?     Have  clearly  in  mind  the  origin  of  each  class. 

3.  Define  system,  series,  formation,  as  applied  to  rock 
divisions,  and  era,  period,  and  epoch,  as  applied  to  the 
divisions  of  geologic  time. 

4.  Note  the  meanings  of  the  various  colors  on  the  Areal 
Geology  Sheet. 

5.  On  the  Areal  Geology  Sheet,  note  carefully  the  con- 
ventions (symbols)  for  stratified  rocks;  for  igneous  rocks; 
for  metamorphic  rocks;  and  for  surface  formations,  such 
as  glacial  drift,  alluvium,  etc. 

6.  Notice  that  the  Areal  Geology  Sheet  shows  topography, 


10        STRUCTURAL  AND  HISTORICAL  .GEOLOGY 

as  well  as  the  areas  where  the  various  rock  formations  come 
to  the  surface. 

7.  How  are  faults  shown  on  geologic  maps  ? 

8.  Draw    diagrams    showing    at    least    two    types    of 
unconformity. 

9.  List  the  geological  events  recorded  by  the  diagrams  in  8. 

10.  a)    Study    the   legend    on  the  Areal   Geology  Sheet 
carefully. 

b)  Note  the  chronological  order  of  the  different 
formations,  as  given  in  the  legend  (oldest  at  bottom  of 
column). 

11.  Explain  what  is  meant  by  dip  and  strike.     How  are 
they  shown  on  the  Areal  Geology  Sheet  ? 


EXERCISE  II 

FOLIOS  SHOWING  HORIZONTAL  OR  NEARLY 
HORIZONTAL  SEDIMENTARY  BEDS 

I.  FOLIOS  TO  BE  STUDIED 

Amity,  Pa.  Lancaster-Mineral  Point,  Wis. 

Buckhannon,  W.  Va.  Sewanee,  Tenn. 

Charleston,  W.  Va.  Washington,  D.  C. 

Coalgate,  Ok.  (I.  T.)  Waynesburg,  Pa. 
Elkland-Tioga,  Pa. 

II.  OUTLINE  FOR  STUDY 

Note. — Students  in  more  elementary  and  briefer  courses 
omit  questions  marked  **,  and  answer  in  writing  questions 
marked  *. 

Students  in  more  advanced  courses  study  all  questions, 
and  answer  in  writing  those  marked  *  and  **. 

A.  General  Questions 

*1.  Draw  a  diagram  showing  how  the  relative  ages  of  beds 
can  be  told  by  their  positions  with  reference  to  one  another. 
2.  If  perfectly  horizontal  strata  underlie  a  perfectly  flat 
surface,  how  many  formations  will  outcrop  ? 

*3.  a)  Given  a  flat  surface  underlain  by  horizontal  strata, 
each  stratum  50  feet  thick,  in  which  there  are  valleys  not 
more  than  25  feet  deep ;  how  many  strata  will  outcrop  ? 

b)  Given  the  same  conditions  as  in  a)  except  that  t{ie 
11 


12        STRUCTURAL  AND  HISTORICAL  GEOLOGY 

valleys  are  60  feet  deep:  What  strata  will  outcrop,  and  in 
what  topographic  positions  ? 

c)  If  the  valleys  are  400  feet  deep,  how  many  strata 
will  outcrop  ? 

*4.  If  strata  are  perfectly  horizontal  and  uniform  in 
thickness,  what  relation  should  there  be  on  a  geologic  map 
between  boundaries  of  formations  and  contour  lines  ? 

*5.  Would  the  answer  to  4  hold  if  the  horizontal  beds 
were  unconformable  ? 

**6.  What  are  the  shapes  of  outcrops  of  uniformly  tilted 
beds  on  a  flat  surface? 

**7.  Explain  how  thickness  of  horizontal  beds  can  be 
determined  from  geologic  maps.  Does  this  method  involve 
any  error  if  the  beds  have  a  dip  ? 

**8.  If  strata  have  a  slight  dip,  how  can  it  be  detected  and 
measured  from  a  geologic  map  ? 

B.  Questions  on  Folios 

Washington  Folio: 

*1.  Compare  the  distribution  of  outcrops  of  the  sedimen- 
tary formations  (Historical  Geology  Sheet)  with  the  distri- 
bution of  the  contours.  What  inference  concerning  the 
structure  of  these  formations  can  be  drawn  from  this 
comparison  ? 

**2.  Determine  the  elevation  of  the  base  of  formation  Nl, 
base  and  top  of  Nc,  and  the  top  of  Ep,  in  the  western  and 
eastern  portions  of  the  area  shown  on  the  map.  The 
inference  ? 

**3.  What  is  the  thickness  of  Nl  and  Nc  as  shown  by  the 
Historical  Geology  Sheet  ?  Considering  your  answer  to  2, 
is  the  estimate  without  possible  error? 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        13 

4.  In  what  ways  may  the  varying  thickness  of  Nc  be 
interpreted  ? 

5.  What  inference  may  be  made  from  the  distribution  of 
Nl?  . 

*6.  How  may  the  failure  of  Kp  to  underlie  Nl  in  some 
places,  as  at  Wesley  Heights  (2J  miles  northwest  of  Wash- 
ington) be  explained  ? 

**7.  At  what  times  was  the  region  subjected  to  subaerial 
erosion,  as  shown  by  the  relations  of  the  formations  ? 

Sewanee  Folio: 

1.  Note  the  distribution  of  outcrops. 

2.  Note  the  position  of  the  beds. 

**3.  Determine  from  the  Areal  Geology  Sheet  the  thickness 
of  formations  Cw  and  Cl,  at  a  point  six  miles  north-north- 
west  of  Jasper,  in  the  southeastern  part  of  the  area. 
**4.  Explain  the  areas  of  Cw  surrounded  by  Cl.     Give  all ' 
conceivable  explanations.     Which  is  correct  ? 

Charleston  Folio: 

**1.  From  the  Historical  Geology  Sheet,  determine  (1)  the 
direction  of  dip,  and  (2)  as  nearly  as  possible  its  amount. 

Buckhannon  Folio: 

*1.  Explain  the  arrangement  of  outcrops  along  the  bottom 
of  the  valley  of  Buckhannon  River. 

Coalgate  Folio: 

*1.  Determine  the  stratigraphic  relations  of  formation  Ng. 

*2.  The  cause  of  the  belted  arrangement  of  the  Carbonif- 
erous formations  in  the  northern  half  of  the  area  ? 
**3.  Account  for  the  varying  width  of  the  outcrops  of  some 
of  these  formations,  notably  Ct. 


14       STRUCTURAL  AND  HISTORICAL  GEOLOGY 

Elkland-Tioga  Folio  (Tioga  Sheet): 

**1.  Study  the  distribution  of  outcrops  east  of  Tioga,  in 
relation  to  the  distribution  of  contour  lines.  The  inference  ? 
Test  your  conclusion  by  reference  to  the  Structure  Section 
Sheet. 

Waynesburg  Folio: 

*1.  Notice  the  dendritic  shapes  of  the  outcrops.  The 
inference  ? 

*2.  Determine  the  elevation  of  the  top  of  formation  Cw  at 
several  points  along  the  parallel  of  39°  50',  and  along  the 
meridian  of  80°  10'.  What  inference  from  the  above  ? 

3.  Determine  the  thickness  of  formation  Cw  in  the  extreme 
northeast  corner  of  the  central  rectangle.1 

Amity  Folio: 

1.  Note  the  distribution  and  shapes  of  the  outcrops. 

2.  **a)  Explain  the  outcrop  of  formation  Cm  surrounded 
by  Cw  (eastern  part  of  central  rectangle). 

*b)  Explain  outcrops  of  Cg  surrounded  by  Cw  in 
southeast  part  of  central  rectangle. 

*3.  What  are  the  stratigraphic  relations  of  Qcm  ? 
**4.  In  what  direction  do  the  strata  dip  ? 
**5.  Determine,  at  least  roughly,  the  amount  of  dip. 

Lancaster-Mineral  Point  Folio: 

1.  Note  the  dendritic  character  of  the  outcrops. 

2.  Study   the   Areal    Geology   Sheet   for   thickness   and 
structure  of  beds. 

1  The  name  rectangle  is  applied  to  the  smallest  area  bounded  by 
parallels  and  meridians  on  a  map. 


EXERCISE  III 

FOLIOS    SHOWING    DEFORMATION    OF    SEDI- 
MENTARY BEDS  WITHOUT  FAULTING 

I.  FOLIOS  TO  BE  STUDIED 

Accident-Grantsville,  Md.  Lancaster-Mineral  Point, 

Bristol,  Va.  Wis. 

Coalgate,  I.  T.  (Ok.)  Newcastle,  Wyo. 
Franklin,  W.  Va. 

H.  OUTLINE  FOR  STUDY 

See  Note,  p.  11. 

1.  Compare  the  Areal  Geology  Sheet  of  the  Lancaster- 
Mineral  Point  folio  with  the  corresponding  maps  of  the  rest 
of  the  folios  of  the  list  assigned.  Explain  why  most  of  the 
outcrops  shown  on  the  former  have  a  dendritic  arrangement, 
while  the  formations  shown  on  the  other  maps  outcrop  in 
belts. 

Newcastle  Folio: 

1.  Study  the  cases  of  simple,  but  pronounced  deformation 
shown  by  the  structure  sections. 

2.  Note  the  type  of  deformation  shown  by  the  structure 
sections. 

Bristol  Folio: 

*1.  Explain  the  belted  arrangement  of  the  outcrops. 
*2.  How   much    may  be  inferred  from  the  topographic 
map  concerning  (1)  the  kinds  of  rock  which  underlie  the 
region,  and  (2)  their  structure  ?  * 

15 


16       STRUCTURAL  AND  HISTORICAL  GEOLOGY 

*3.  From  the  Historical  Geology  Sheet,  determine  the 
position  of  the  beds  between  Cornsville  (center  of  west 
central  rectangle)  and  Early  Grove  (northwest  part  of  south 
central  rectangle). 

**4.  Account  for  the  looped  outcrop  of  Cn  in  the  northwest 
rectangle. 

**5.  The  structure  of  the  beds  in  the  basin  of  Brumley 
Creek,  northeast  rectangle. 

*6.  State  a  law  for  determining  the  direction  of  dip  of  strata 
from  geologic  maps. 

*7.  How  may  anticlines  be  distinguished  from  synclines  on 
geologic  maps  ? 

*8.  Given  a  formation  with  a  dip  of  20°,  outcropping  on  a 
flat  surface: 

a)  Increase  the  dip  to  45°;  does  the  outcrop  increase 
or  decrease  in  width  ? 

b)  Decrease  the  dip  to  1°;  does  the  outcrop  increase  or 
decrease  in*width  ? 

c)  If  the   dip   becomes   90°,   what   relation  is   there 
between  the  width  of  the  outcrop  and  the  thickness  of  the 
formation  ? 

*9.  Given  a  horizontal  formation  outcropping  on  a  hillside 
which  has  a  slope  of  20°: 

a)  Decrease  the  slope  of  the  hill  to  5°;  does  the  outcrop 
increase  or  decrease  in  width  ? 

b)  Increase  the  slope  of  the  hill  to  60°;  does  the  outcrop 
increase  or  decrease  in  width  ? 

c)  Increase  the  slope  of  the  hill  to  90°;  what  relation  is 
there  between  the  width  of  the  outcrop  and  the  thickness 
of  the  formation.  ? 

**10.  Formulate  a  law  which  will  express  the  relation  be- 
tween slope  of  surface,  dip  of  strata,  and  width  of  outcrop. 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        17 

Coalgate  Folio:  * 

*1 .  Explain  the  belted  arrangement  of  the  outcrops  of  the 
several  formations. 

*2.  In  what  direction  do  the  strata  in  the  north  part  of  the 
area  dip  ? 

*3.  Why  are  the  outcrops  of  Ct,  Cst,  Csn,  etc.,  broader  in 
the  northeast  than  in  the  west  central  part  of  the  district  ? 
Test  your  conclusion  by  reference  to  the  Structure  Section 
Sheet. 

*4.  Account  for  the  area  of  Cm  within  Cs,  east  central 
part  of  map. 

**5.  Determine   from  the   Historical   Geology   Sheet    the 
structure   of  the  beds  northwest   of  North  Boggy   Creek 
(southeast  part  of  map),  along  the  line  BB.     Test  your 
onclusion  by  reference  to  the  Structure  Section  Sheet. 
**6.  Why  does  the  outcrop  of  Cm  disappear  to  the  north- 
east of  Cottonwood  ?     If  the  surface  rose  in  that  direction, 
would  there  be  an  alternative  explanation  ? 
**7.  Why  is  the  Cb  area  southeast  of  Coalgate  not  con- 
nected with  the  Cb  area  to  the  northeast  ? 
**8.  Show   by   diagrams    how    a    belted   arrangement    of 
outcrops  may  appear  on  a  hillside,  without  a  tilting  of  the 
beds. 

Franklin  Folio: 

1.  What  inference  as  to  structure  may  be  made  from  the 
topographic  map  ? 

2.  The  character  of  Stc,  as  suggested  by  the  structure 
sections  ? 

*3.  From  the   details  of  the  eastern  slope  of  the  anti- 
clinal  mountain   shown  in  section  AA,  Structure  Section 
2 


18        STRUCTURAL  AND  HISTORICAL  GEOLOGY 

Sheet,  what  inference  may  be  made  concerning  the  relative 
hardness  of  the  beds  ? 

4.  Study  the  structure  sections  for  the  relation  between 
the  degree  of  folding  and  the  amount  of  erosion. 

*5.  a)  How  may  the  looped  arrangement  of  the  Sen -and 
Sr  outcrops  near  Elkhorn  Rock  be  interpreted  (northeast 
part  of  Areal  Geology  Sheet)  ? 

b)  What  does  the  appearance  of  Sen  and  Sr  east 
of  Mill  Gap  mean  ?  (The  topographic  map  will  be  of  as- 
sistance in  answering  this  question.) 

**6.  How  are  the  small  areas  of  SI  just  west  of  the  South 
Fork  of  the  Potomac  River  in  the  northeast  rectangle,  to  be 
interpreted  ? 

**7.  Interpret  the  loop-shaped  outcrops  of  Sr  northwest 
of  Franklin. 

*8.  Interpret  the  irregular  contact  between  the  Devonian 
and  Carboniferous  outcrops  in  the  northwest  part  of  the 
map. 

*9.  Account  for  the  isolated  outcrop  of  Cpo,  in  Dh,  di- 
rectly west  of  Onego  (N.  W.  rectangle) . 
**10.  Account  for  the  various  outcrops  along  the  line  of 
Reed  Creek  (western  part  of  central  rectangle). 
**11.  The  date  of  the  folding  of  the  beds  of  this  area? 
**12.  Show  by  a  series  of  drawings  the  effects  of  various 
topographic  forms  upon  the  shapes  of  outcrops. 

Accidenl-Grantsmlle  Folio: 

1.  Study  the   strip   of   Cpo  extending  in   a   northeast- 
southwest  direction  across  the   center  of  the   Grantsville 
sheet: 
*a)  Is  the  formation  dipping  or  horizontal  ? 

b)  What  of  the  amount  of  dip  ? 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        19 

**c)  Determine  the  direction  of  dip  by  the  shape  of  the 
outcrop  at  stream  crossings,  without  reference  to  the  age  of 
the  formations. 

**2.  Determine  the  structure  of  Dj  (Grantsville  Sheet)  by 
the  relations  between  streams  and  the  shapes  of  the  out- 
crops on  either  side. 


EXERCISE  IV 

FOLIOS  SHOWING  DEFORMATION  OF  SEDI- 
MENTARY BEDS  ACCOMPANIED  BY  FAULTING 

I.  FOLIOS  TO  BE  STUDIED 

Briceville,  Tenn.  Pocahontas,  Va. 

Engineer  Mountain,  Colo.  Roan  Mt.,  Tenn. 

Mercersburg-Chambers-  Tahlequah,  I.  T.  (Ok.) 
burg,  Pa. 

II.  OUTLINE  FOR  STUDY 

See  Note,  p.  11. 

A.  Preliminary  Questions: 

*1.  Show  by  diagrams  the  difference  between  normal  and 
reversed  faults. 

*2.  Draw  a  diagram  of  a  fault,  and  designate  by  letters 
the  meaning  of  the  following  terms: 

a)  Fault  scarp.  f)    Heave. 

b)  Upthrow  side.  g)  Dip. 

c)  Downthrow  side.  h)  Hade. 

d)  Fault  plane.  i)    Hanging  wall. 

e)  Throw.  j)   Foot  wall. 

3.  Which  one  of  the  features  mentioned  in  2  appears  on 
topographic  maps  ?  The  others  can  be  studied  on  geologic 
maps,  structure  sections,  and  in  the  field. 

20 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        21 

*4.  a)  After  faulting,  will  the  upthrow  or  the  downthrow 
side  suffer  more  erosion  ? 

b)  How  can  the  upthrow  side  be  distinguished  from 
the  downthrow  side  on  a  geologic  map  ? 

5.  Define  the  terms  strike-,  dip-,  and  oblique- faults. 
**6.  Show  by  diagram  how  the  outcrop  of  a  dipping  bed 
is  shifted  by  erosion. 

7.  If  dipping  beds  are  faulted,  and  the  upthrow  side  is 
eroded  more  than  the  downthrow  side,  the  outcrop  of  the 
dipping  beds  will  be  shifted  farther  in  the  direction  of  dip  on 
the  upthrow  side,  than  on  the  downthrow  side. 

**Illustrate  this  point  by  diagram  or  simple  maps,  in 
the  case  of  both  dip  and  oblique  faults. 

**8.  Draw  a  simple  sketch  map  showing  offset  with  overlap. 
Designate  the  upthrow  side. 

**9.  Show  by  diagrams  how  outcrops  may  be  cut  out, 
duplicated,  narrowed,  and  broadened,  as  a  result  of  strike 
faults. 

10.  Do  reversed  faults  occur  more  commonly  with  hori- 
zontal or  with  dipping  beds  ?     Explain. 

B.  Questions  on  Folios 

Briceville  Folio: 

1.  Are  the  strata  horizontal  or  folded  in  the  southeast 
part  of  the  area  ?     In  the  west  and  northwest  parts  ? 
*2.  Locate  faults  on  the  Areal  Geology  Sheet. 

3.  Are  most  of  the  faults  strike,  dip  or  oblique  faults  ? 
*4.  Are  the  faults  normal  or  reversed,  as  shown  in  the 
structure  sections  ? 

**5.  From  what  directions  were  the  forces  probably 
applied  which  resulted  in  the  folding  and  faulting  of  the 
region  ? 


22        STRUCTURAL  AND  HISTORICAL  GEOLOGY 

**6.  Determine    as   nearly   as    possible    the    date   of    the 
faulting. 

Pocahontas  Folio: 

*1.  From  the  Areal  Sheet,  work  out  in  as  much  detail  as 
possible  the  structure  at  Burke  Garden,  in  the  south- 
western part  of  the  map. 

**2.  What  is  the  structure  at  Round  Mountain  (north-east- 
ern part  of  south  central  rectangle)  ? 

*3  What  is  the  structure  at  Nye  Cove,  in  the  south- 
western part  of  the  central  rectangle  ? 

**4.  Account  for  the  sequence  of  outcrops  along  the  val- 
ley of  Roaring  Fork,  southwest  of  Burke  Garden. 

*5.  What  is  the  direction  of  dip  of  the  formation  Cpc, 
northwest  of  Sharon  Springs,  south  central  rectangle  ? 

*6.  Account  for  the  juxtaposition  of  Cpc  and  CSs  in 
the  southeastern  part  of  the  map. 

7.  Account  for  the  protrusion  of  Devonian  into  Car- 
boniferous 5  miles  northeast  of  Effna  in  the  south  central 
rectangle. 

**8.  Explain  the  peculiar  break  in  the  outcrops  of  Sr  and 
SDg,  southeast  of  Effna. 

9.  How  may  the  crenate  outline  of  many  of  the  outcrops 
be  explained  ? 

Tahlequah  Folio: 

1 .  What  is  the  general  structure  of  the  formations  ? 
**2.  Explain   the  failure  of  the  Devonian   beds   to  occur 
between  Ssc  and  Cbn  in  the  small  valley  2  miles  north  of 
Bunch  in  the  south  central  part  of  the  central  rectangle. 

3.  Explain    he  outcrop  of  Ot  in  the  valley  of  Barren 
Fork  (north  central  part  of  map). 
*4.  Explain  the  isolated  outcrops  of  Cwl  and  older  Car- 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        23 

boniferous  beds  in  the  central  and  north  central  parts  of 
the  region. 

*5.  Determine  the  downthrow  side  of  the  several  faults  in 
the  western  part  of  the  area. 

**6.  Explain  the  small  outcrop  of  DC  in  the  center  of  the 
northeast  rectangle.  Note  the  topographic  expression 
of  DC. 

*7.  a)  Which  is  the  downthrow  side  of  the  fault  cutting 
the  small  hill  five  miles  due  northeast  of  Wauhillan  (north 
central  rectangle)  ? 

b)  Same  for  the  fault  cutting  Chi  seven  miles  southeast 
of  Wauhillan. 

**8.  Are  the  faults  of  this  district  probably  normal  or 
reversed  ?  Why  ? 

J/.  r 

Engineer  Mountain  Folio: 

**1.  Study  the  faulted  area  in  the  east  central  part  of  the 
northeast  rectangle,  as  follows: 

a)  Determine  the  upthrow  side  of  each  of  the  two  faults 
cutting  De. 

b)  Having  determined  the  upthrow  sides  of  the  faults, 
in  what  direction  does  De  dip  ? 

c)  How  many  periods  of  faulting  have  there  been? 
Give  dates. 

d)  Explain    the    disappearance  of    De  and    DCo  to 
the  north. 

2.  Determine  the  upthrow  sides  of  the  two  faults  in  the 
southeastern  part  of  the  central  rectangle. 

Mercersburg-Chambersburg  Folio: 

*1.  Which  is  the  downthrow  side  of  the  fault  in  the 
northwestern  part  of  the  central  rectangle,  and  the  south- 


24       STRUCTURAL  AND  HISTORICAL  GEOLOGY 

eastern  part  of  the  north  central  rectangle,  Chambersburg 
Areal  Geology  Sheet? 

2.  What  is  the  direction  of  dip  of  Cc  and  Osh  ? 
**3.  Follow  the   outcrop   Oc  along    the   strike  from   St. 
Thomas  (southern  part  of  northeast  rectangle,  Mercersburg 
Sheet)  to  the  south  edge  of  the  map.     Explain  in  detail  all 
discontinuities. 

**4.  Explain  the  outcrop  of  Oc  one  mile  southwest  of 
St.  Thomas. 

**5.  The  fault  line  shown  in  the  southwestern  part  of  the 
Mercersburg  sheet,  running  between  Cove  Mountain  and 
Little  Cove  Creek,  is  in  contact  with  several  different  forma- 
tions in  its  course.  Explain. 

**6.  Determine  the  amount  of  throw  of  the  fault  between 
Scy  and  Do  (S.  W.  part  of  Mercersburg  Sheet),  as  nearly 
as  possible. 

**7.  Work  out  the  sequence  of  faulting  south  of 
Mercersburg. 

Roan  Mountain  Folio: 

1.  Notice    the    peculiar    courses  of    the    faults    around 
Cherokee  and  Buffalo  Mountains  (west  central  rectangle); 
give  possible  explanations. 

2.  See    structure    sections    and     text    for    correct     ex- 
planation of  1. 


EXERCISE  V 

FOLIOS  SHOWING  VARIOUS  PHASES  OF 
VULCANISM 

I.  FOLIOS  TO  BE  STUDIED 

Elmoro,  Colo.  Spanish  Peaks,  Colo. 

Fort  Benton,  Mont.  Sundance,  Wyo. 

Passaic,  N.  J.  Walsenburg,  Colo. 
Port  Orford,  Ore. 

H.  OUTLINE  FOR  STUDY 

See  Note,  p.  11. 

A.  General  Questions 

1.  What  are  the  more  common  igneous  rocks  named  in 
the  legends  of  these  folios  ? 

2.  What  is  the  origin  of  igneous  rocks  ? 

3.  Name  three  groups  of  igneous  rocks,  classified  accord- 
ing to  the  size  of  crystals. 

*4.  From  the  legends  of  the  folios,  choose  formations  in 
which  the  rocks  have  resulted  from  the  cooling  of  intruded 
lava;  of  extruded  lava.  (Have  in  mind  the  relation  between 
the  rate  of  cooling  and  the  size  of  the  crystals;  also  the  re- 
lation between  the  rate  of  cooling  of  extruded  and  intruded 
lavas.) 

5.  Explain  how  intrusive  igneous  rocks  may  come  to  be 
at  the  surface. 

*6.  Draw  a  diagram  or  a  series  of  diagrams  showing  the 

25 


26        STRUCTURAL  AND  HISTORICAL  GEOLOGY 

various  forms  assumed  by  igneous  rocks,  both  intrusive  and 
extrusive.  Apply  the  proper  geologic  name  to  each  of  these 
forms. 

**7.  How  may  the  age  of  igneous  rocks  be  determined,  if 
they  are  associated  with  stratified  rocks  of  known  age? 
Does  the  law  of  super-position  always  apply  in  this  connec- 
tion ?  Does  it  ever  apply  ?  Explain. 

B.  Question  on  Folios 
Elmoro  Folio: 

1.  What  is  the  age  of  the  igneous  rock?     Test  the  con- 
clusions reached  from  the  study  of  the  Historical  Geology 
Sheet,   by  reference  to  the  Structure  Section  Sheet,   and 
finally  to  the  legend. 

2.  What  evidence  is  there  of  erosion  since  the  outflow 
of  the  lava  ? 

3.  Has  the  lava  accelerated  or  retarded  erosion  ?     Rea- 
sons for  answer. 

4.  What  inference  can  be  made  as  to  the  origin  of  the 
lake  basins  on  the  top  of  the  Raton  Mesa  ? 

Walsenburg  Folio: 

1.  Study  carefully  the  series  of  dikes  shown  on  the  Ig- 
neous Geology  Sheet  southwest  of  Rouse,  in  the  southern 
part  of  the  map.  Compare  with  the  Topographic  Sheet. 

*2.  Explain  the  looped  outcrops  of  lip,  elp,  and  bs  (south 
central  rectangle). 

**3.  Which  is  older,  elp  or  lip,  central  part  of  central 
rectangle  ? 

*4.  Note  the  dike  in  the  extreme  south  central  part  of 
the  map.  Which  took  place  first,  the  faulting  or  the  in- 
trusion of  the  dike  ? 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        27 

**5.  If  the  east  side  of  the  fault  mentioned  under  d)  is  the 

downthrow  side,  which  way  does  the  dike  dip  ? 

**6.  What  was  the  date  of  extrusion  of  snip  relative  to  the 

faulting,  and  to  Nn  (west  central  part  of  map)  ? 

**7.  What  are  the  relative  ages  o'f  bs  and  Nn  in  the  extreme 

west  central  part  of  the  area. 

Spanish  Peaks  Folio: 

1.  Determine  from  the  Historical  Geology  and  Structure 
Section  sheets  the  dates  of  the  volcanic  activity. 

2.  How    do    the    many    dikes    of    the    area    affect    the 
topography  ? 

**3.  Might  the  present  surface  relations  of  the  Creta- 
ceous and  Eocene  beds  east  of  the  mountains  hold,  (1)  if 
the  beds  were  horizontal  ?  (2)  If  they  dipped  to  the  west  ? 
(3)  If  they  dipped  to  the  east  ? 

**4.  How  has  the  intrusion  of  ad  affected  Eh  in  the  south- 
west part  of  the  northwest  rectangle  ?  (See  Structure  Sec- 
tion Sheet  and  legend.) 

Port  Orford  Folio: 

1.  Note  the  kinds  of  intrusive  rocks. 

*2.   Determine    from    the    Areal    and    Structure    Section 
sheets  the  age  of  the  igneous  rocks. 

*3.  How  many  times  and  when  were   the    sedimentary 
beds  of  the  area  deformed  ? 

**4.  What  hypotheses  may  be  advanced  to  account  for  the 
the  isolated  patches  of  sedimentary  rocks  within  igneous 
rock  areas,  shown  on  the  Areal  Geology  Sheet  ?     Test  your 
theories  by  reference  to  the  structure  sections. 
Fort  Benton  Folio: 

1.  Study   the   maps   of   this   folio   for  examples  of  lac- 
coliths and  bysmaliths, 


28       STRUCTURAL  AND  HISTORICAL  GEOLOGY 

**2.  Explain  the  curvilinear  areas  of  igneous  rock,  as 
about  Taylor  Peak  (south  central  part  of  map) . 

*3.  Is  the  dip  of  the  beds x  greater  or  less  than  the 
gradient  of  the  streams  on  the  north  slope  of  the  Little 
Belt  Mountains  ? 

**4.  In  what  ways  may  the  absence  of  Proterozoic 
(Algonkian),  Ordovician,  and  Silurian  formations  be 
accounted  for  ? 

Sundance  Folio: 

1.  Study  the  laccoliths  of  this  region.     See  Areal  Geology 
and  Structure  Section  sheets. 

Passaic  Folio: 

1.  Note  the  forms  of  the  outcrops  of  the  igneous  rocks. 
**2.  How  could  you  tell,  in  the  field,  whether  Trw   and 
Trp  are  dikes,  sills,  or  surface  flows  ? 

3.  Study   the  illustrations.     What   causes   the   columns 
shown  in  Fig.  30  ? 


EXERCISE  VI 
FOLIOS  SHOWING  METAMORPHIC  ROCKS 

I.  FOLIOS  TO  BE  STUDIED 

Bradshaw  Mountains,  Ariz.      Penobscot  Bay,  Me. 
Colfax,  Cal.  Pyramid  Peak,  Cal. 

Cranberry,  N.  C.  Spanish  Peaks,  Colo. 

H.  OUTLINE  FOR  STUDY 

See  Note,  p.  11. 

The  processes  of  metamorphism  should  be  well  in  mind 
before  the  study  of  the  folios  is  undertaken. 

A.  General  Questions 

*1.  What  is  the  relation  between  metamorphic  rocks  and 
such  diastrophic  forces  as  those  which  produce  folds  and 
faults  ? 

*2.  What  relation  is  there  between  vulcanism  and  meta- 
morphism ?  See  the  Eh  and  Em  formations  around  West 
Spanish  Peak  (Spanish  Peaks  folio) . 

*3.  What  sequence  of  events  is  recorded  by  a  metamorphic 
formation,  such  as  mica  schist,  underlying  a  sedimentary 
formation  which  has  not  been  metamorphosed  ? 

B.  Questions  on  Folios 
Colfax  Folio: 

1 .  Note  the  various  kinds  of  metamorphic  rocks  shown. 
*2.  From   the   metamorphic  rocks   of  the   legend,  desig- 

29 


30       STRUCTURAL  AND  HISTORICAL  GEOLOGY 

nate  one  formation  which  is  meta-sedimentary,  and  one 
which  is  meta-igneous. 

*3.  What  can  be  said  of  the  relative  ages  of  sp  and  am  ? 
Refer  to  the  Historical  Geology  Sheet  and  the  Structure 
Section  Sheet. 

**4.  What  are   the  relative  ages  of  sp   and  pr  (northern 
part  of  south  central  rectangle)  ? 

**5.  From  the  Structure  Section  Sheet,  determine  the  date 
or  dates  of  deformation  of  the  beds. 

**6.  At  what    time    or   times    were    the    rocks    metamor- 
phosed ? 

7.  What  is  the  meaning  of  the  small  patches  of  Na 
just  north  of  the  American  River  (central  and  east  central 
rectangles)  ? 

Pyramid  Peak  Folio: 

1.  Note  the  various  kinds  of  metamorphic  rocks  in 
this  area. 

**2.  The  date  or  dates  of  deformation  of  the  beds  ? 
**3.  The  probable  time  or  times  of  metamorphism  ? 

4.  Is  there  evidence  of  the  former  greater  extent  of  the 
igneous  formations  ? 

Cranberry,    Bradshaw    Mountains,    and    Penobscot    Bay 
Folios: 

1.  In  each  of  these  folios,  study  the  various  meta- 
morphic rocks  shown,  their  relations  to  each  other,  and  their 
relations  to  the  igneous  rocks. 

**2.  From  the  facts  worked  out  in  a),  determine  the  dates 
of  metamorphism  in  each  of  these  regions. 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        31 

B.  SYSTEMIC  SERIES 

Having  become  familiar  in  the  preceding  exercises  with 
geologic  folios,  and  with  some  of  the  principles  involved  in 
their  interpretation,  and  having  learned  to  read  something 
of  geologic  history  from  the  rock  record  as  shown  on  the 
folios,  we  turn  to  a  study  of  the  various  systems  of  the 
geologic  column  in  North  America.  These  systems  will  be 
considered  in  chronological  order.  The  study  of  the  fol- 
lowing exercises  will  result  in  (1)  greater  efficiency  in  the 
interpretation  of  geologic  maps,  (2)  greater  familiarity  with 
the  principles  involved  in  the  development  of  the  many 
structural  features  shown  by  the  maps,  (3)  a  better  working 
knowledge  of  the  methods  employed  in  reading  the  history 
of  the  earth  from  'the  record  of  the  rocks,  (4)  an  introduction 
to  the  history  of  the  various  regions  of  the  United  States  in 
the  different  eras  and  periods  of  geologic  time,  and  (5)  some 
degree  of  familiarity  with  the  general  history  of  the  earth. 
These  exercises  should  emphasize  the  principles  and  facts 
developed  in  the  class-room. 


EXERCISE  VII 

ARCHEOZOIC  AND  PROTEROZOIC  (ALGONKIAN) 

I.  FOLIOS  TO  BE  STUDIED 

Asheville,  N.  C.  Mercersburg-Chambersburg, 
Bald  Mountain-Dayton,  Wyo.          Pa. 

Bisbee,  Ariz.  Needle  Mountains,  Colo. 

Cloud  Peak-Fort  McKinney,  Ouray,  Colo. 

Wyo.  Parker,  S.  D. 

Cranberry,  N.  C.  Passaic,  N.  J. 

El  Paso,  Tex.  Patuxent,  Md. 

Franklin  Furnace,  N.  J.  Penobscot  Bay,  Me. 

Globe,  Ariz.  Rico,  Colo. 

Harpers  Ferry,  Va.  Sundance,  Wyo. 

Holyoke,  Mass.  Tishomingo,  Ok. 

Menominee,  Mich.  Washington,  D.  C. 

H.  DIRECTIONS 

In  answering  the  questions  below,  most,  if  not  all,  of  the 
above  folios  should  be  studied.  If  the  questions  cannot  be 
answered  satisfactorily  from  the  geologic  maps  alone,  the 
text  of  the  folios  should  be  studied.  Note  at  the  outset  in 
which  geologic  province  of  the  United  States  the  area  of 
each  folio  lies. 

See  Note,  p.  11. 

32 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        33 

III.  QUESTIONS 

1.  Outline  the  general  distribution  of  the  Archean  and 
Proterozoic  (Algonkian)  as  shown  by  the  folios. 

2.  Note  the  kinds  of  rocks  (see  legends)  in  the  Archean 
and  Proterozoic  (Algonkian)  in  each  region. 

3.  Explain  the  forms  of  the  outcrops,   such  as  narrow 
belts,  broad  areas,  etc. 

4.  Note  the  topographic  positions  of  the  outcrops. 

*5.  Make  a  comparative  study  of  the  structures  and 
structural  relations  of  the  Archean  and  Proterozoic  in  the 
following  regions,  and  illustrate  with  diagrams  the  different 
relationships  shown: 

a)  New  England  (Holyoke  and  Penobscot  Bay  folios). 

b)  Piedmont  Plateau  (Patuxent  and  Washington  folios) . 

c)  Appalachian  Mountains  (North  Carolina  folios). 

d)  The  Southern  Interior  (El  Paso  and  Tishomingo 
folios). 

e)  The  Northern  Great  Plains  (Parker  and  Sundance 
folios). 

f)  The  San  Juan  Mountains  (Colorado  folios). 

g)  The  Bighorn  Mountains  (Bald  Mountain-Dayton 
and  Cloud  Peak-Fort  McKinney  folios). 

h)  The  Arizona  Region  (Globe  and  Bisbee  folios). 
*6.  State     briefly,     but     comprehensively,     the     geologic 
history  recorded  in  each  relationship  shown  by  the  above 
series  of  diagrams. 

**7.  State,  if  you  can,  whether  or  not  the  pre-Cambrian 
rocks  were  ever  covered  by  later  deposits  in  each  of  the 
regions  given  in  5. 

8.  How  has  vulcanism  affected  the  pre-Cambrian  rocks 
in  the  different  regions?  Fix  the  date  of  vulcanism  as 
closely  as  possible  in  each  case. 

3 


34        STRUCTURAL  AND  HISTORICAL  GEOLOGY 

9.  The  metamorphic  rocks: 

a)  Date  of  metamorphism,  if  determinable  ? 

b)  Mode  of  metamorphism  ? 

c)  The  antecedents  of  the  metamorphic  rocks  ? 

*10.  Work  out  the  physical  history  of  the  Menominee 
region. 


EXERCISE  VIII 

CAMBRIAN 
I.  FOLIOS  TO  BE  STUDIED 

A.  Folios  for  Elementary  and  Briefer  Courses 

Absaroka,  Wyo.  Gadsden,  Ala. 

Bald  Mountain-Dayton,  Harpers  Ferry,  Va. 

Wyo.  Morristown,  Tenn. 

Bristol,  Va.  Philadelphia,  Pa. 

Clifton,  Ariz.  Tazewell,  Va. 

Franklin  Furnace,  N.  J.  Tishomingo,  Ok.  (I.  T.) 

B.  Additional  Folios  for  More  Advanced  Courses 

Asheville,  N.  C.  Mercersburg-Chambers- 
El  Paso,  Texas.  burg,  Pa. 

Estillville,  Ky.  Needle  Mountains,  Colo. 

Fort  Benton,  Mont.  Pisgah,  N.  C. 

Greene ville,  Tenn.  Rico,  Colo. 

Holyoke,  Mass.  Ringgold,  Ga. 

Maynardville,  Tenn.  Rockland,  Me. 

Menominee,  Mich.  Three  Forks,  Mont. 
Tintic,  Utah. 

H.  DIRECTIONS 

Elementary  Classes. — Study  only  the  folios  of  group  A. 
Study  all  questions,  except  those  marked  **,  and  answer  in 
writing  those  marked  *. 

Advanced  Classes. — Study  all  the  folios  of  groups  A  and 

35 


36        STRUCTURAL  AND  HISTORICAL  GEOLOGY 

B.  Study  all  questions,  and  answer  in  writing  those  marked 
*  and  **.  Maps  of  Group  B  are  to  be  used  especially  in 
answering  the  General  Questions  (p.  42). 

HI.  QUESTIONS 

I.  Eastern  Region 

Franklin  Furnace  Folio: 

1.  What  is  the  general  structure  of  the  Cambrian  beds? 
*2.  Give  in  detail  the  conditions  which  have  caused  the 

gap  in  €h,  in  the  extreme  northwest  corner  of  the  east 
central  rectangle. 

3.  What  is  the  structure  of  Ch  and  COk  in  the  south 
central  rectangle  ? 

**4.  Explain  in  detail  the  distribution  of  €h  in  the  central, 
east  central,  and  northeast  rectangles. 

*5.  What  causes  the  outcrop,  and  the  form  of  the  outcrop, 
of  the  Cambrian  beds  one  mile  east  of  Woodruff  Gap,  in  the 
northwest  part  of  the  south  central  rectangle  ? 

Philadelphia  Folio  (Norristown  and  Germantown  Sheets) : 
*1.  a)  What  is  the  lithological  character  of  the  Cambrian 
rocks  ? 

b)  Describe  the  geographic  conditions  under  which 
these  rocks  were  deposited. 

c)  The  probable  date  of  metamorphism  ? 

2.  With  what  other  systems  of  rocks  are  the  Cambrian 
rocks  associated  ? 

3.  Note  the  bifurcations  of  faults   1   mile  northeast  of 
Radnor  Station,   Norristown  Sheet,   and  J  mile  north  of 
Meadow  Brook,  Germantown  Sheet. 

**4.  a)  Draw  a  structure  section  from  the  final  "a"  of 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        37 

Narcissa,  south  to  the  final  "1"  of  Spring  Mill,  extreme 
east  central  part  of  Norristown  Sheet. 

b)  Name  the  structural  feature  shown  on  the  above 
section. 

c)  Outline  the  physical  history  as  shown  in  the  above 
structure  section. 

Gadsden  Folio: 

1 .  The  position  of  the  beds  ? 

**2.  With  what  systems  do  the  Cambrian  outcrops  come  in 
contact  ?  Explain  these  contacts. 

Tazewell  Folio: 

1.  The  topographic  position  of  the  outcrops? 

2.  Work  out  the  structure  along  the  lines  of  the  sections 
(AA,  BB,  etc.)  from  the  Areal  Geology  Sheet,  then  compare 
with  the  structure  sections. 

*3.  Make  a  northwest-southeast  structure  section  starting 
two  and  one-half  miles  north  of  the  southwest  corner  of  the 
map. 

Bristol  Folio: 

1.  Make  a  detailed  study  of  the  outcrops  in  the  southeast 
part  of  the  map. 

*2.  Make  a  structure  section  from  Bristol,  three  miles 
to  the  northeast. 

**3.  Make  a  northwest-southeast  structure  section  through 
Bristol  and  Tabor,  from  Paperville  on  the  southeast,  to  the 
Carboniferous  on  the  northwest. 

4.  Work  out  in  detail  the  history  of  the  faulted  area  2J 
miles  northeast  of  Lebanon,  in  the  northeast  rectangle. 
**5.  Work  out,  with  diagrams,  the  history  which  has  resulted 
in  the  structure  shown  at  the  contact  of  Carboniferous  and 


38       STRUCTURAL  AND  HISTORICAL  GEOLOGY 

Silurian  west-northwest  of  Bristol,  in  the  third  structure 
section. 

Morristown  Folio: 

1.  Note   the   general    distribution    and   arrangement    of 
Cambrian  outcrops. 

2.  Note  the  widths  of  outcrops  and  their  variations. 

3.  With  what  other  systems  do  the  Cambrian  outcrops 
come  in  contact  ? 

4.  Study  the  succession  of  Cambrian  outcrops  along  the 
lines  of  the  sections  as  indicated  on  the  Areal  Geology  Sheet, 
and  interpret.     After  the  intrepretation  is  made,  study  the 
Structure  Section  Sheet. 

5.  What  is  the  meaning  of  the  shape  of  the  northeast 
termini  of  the  Cambrian  outcrops  near  Morristown  ? 

a)  What  possible  interpretations  ? 

b)  Which  interpretation  is  right  ? 

**6.  What  is  the  structure  determining  the  Cambrian  out- 
crops northwest  of  Flat  Gap  near  the  southwest  corner  of 
the  sheet? 

*7.  Meaning  of  the  Cambrian  extension  (On)  northeast  of 
the  town  of  Flat  Gap,  in  the  southwest  rectangle  ? 
**8.  Meaning  of  the  form  of  the  Crg  outcrop  from  Tate 
Springs  (northwest  of  the  center  of  the  map)  to  its  terminus, 
6  miles  or  so  farther  east  ?     Meaning  of  the  abrupt  terminus  ? 

*9.  Interpret  the  enclosed  €rg  outcrop  at  Mooresburg. 
(Note  the  form  of  the  outcrop  where  crossed  by  the  small 
streams.) 

**10.  Meaning  of  the  Crg  outcrops  to  the  northwest  of  the 
last,  including  the  one  farthest  northwest  in  this  group? 

*11.  Meaning  of  the  Sk  belt  in  €n,  4  miles  and  more 
south-southwest  of  Morristown  ? 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        39 

*12.  Meaning  of  the  eastward  extension  of  the  Cn  outcrop 
three  miles  west-northwest  of  Turley  Mills  (center  of  west 
central  rectangle)  ? 

*13.  What  possible  interpretations  may  be  placed  upon  an 
outcrop  which  varies  in  width  from  point  to  point  ?  Make 
diagrams  to  illustrate. 

14.  What  is  the  meaning  of  abrupt  ends  of  outcrops  like 
that  of  Cn  just  southwest  of  Noeton  (west  central  rectangle)  ? 
**15.  Possible  meanings  of  Cn  outcrops  near  southeast 
corner  of  the  sheet  ? 

16.  Meaning  of  the  great  expansion  in  width  of  Crs  in  the 
northwest  part  of  the  map  ? 

*17.  Make  a  northwest-southeast  structure  section  through 
Noeton  across  the  belts  of  Cambrian  on  either  side. 
**18.  Make  a  similar  section  through  Turley  Mills. 
**19.  Near  the  northeast  corner  of  the  southwest  rectangle, 
a  fault  line  lies  for  a  distance  between  Sk  and  Crt;  traced 
northeast,  it  lies  between  Cm  and  Cn.     Interpret. 
**20.  Note  the  Crs  outcrops  north  and  west  of  Tate  Springs ; 
note  its  termini  in  both  directions.     Note  also  its  relation  to 
other  formations,  and  interpret. 

**21.  In  general,  how  is  a  strike  fault  which  crosses  for- 
mations to  be  interpreted  ? 

22.  Note    the    outcrop    of   Crs    1J    miles    southwest    of 
Mooresburg,  and  its  relations.     What  is  the  explanation  of 
its  presence? 

23.  Explain  the  variations  in  the  width  of  Crg  near  Cobb 
Ford  in  the  northeast  part  of  the  central  rectangle. 

Harpers  Ferry  Folio: 

1.  With  what  systems  do  the  Cambrian  outcrops  come  in 
contact  ? 


40        STRUCTURAL  AND  HISTORICAL  GEOLOGY 

*2.  How  were  these  contacts  brought  about  ? 

3.  What  evidence  is  there  that  the  Cambrian  rocks  were 
once  more  widespread  than  now  ? 

Greeneville  Folio: 

**1.  Explain  fully  the  sequence  of  outcrops  along  the  north- 
east-southwest fault  line  just  east  of  Greeneville,  in  the  north- 
west corner  of  the  south  central  rectangle. 

2.  Explain  the  looped  outcrop  of  Cn  southeast  of  Locust 
Spring  in  the  northwest  corner  of  the  central  rectangle. 

2.   The  Interior  Region 

Tishomingo  Folio: 

*1.  The  meaning  of  the  form  of  the  area  of  Cr,  east  of 
Sylvan,  in  the  west  central  part  of  the  map  ? 

2.  With  what  systems  does  the  Cambrian  come  in  contact  ? 
The  explanation  of  the  diverse  juxtapositions? 

3.  Western  Mountain  Region 

Bald  Mountain-Dayton  Folio: 

1.  What  are  the  indications  that  the  Cambrian  once  had 
a  more  extensive  distribution  than  now? 

*2.  Why  does  Cd  outcrop  more  extensively  in  the  Bald 
Mountain  quadrangle  than  in  the  Dayton  quadrangle  ? 

*3.  Explain  the  looping  of  Cd  to  the  east,  where  crossed  by 
Tongue  River  (northeast  part  of  west  central  rectangle, 
Dayton  Sheet). 

**4.  Give  a  detailed  explanation  of  the  outcrop  and  the 
form  of  the  outcrop  of  Cd,  in  the  northeast  part  of  the  Bald 
Mountain  quadrangle. 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        41 

*5.  What  is  the  structure  of  Cd  at  Porcupine  Canyon,  in 
the  west  central  part  of  the  northwest  rectangle  (Bald 
Mountain  Sheet)  ? 

6.  What  are  the  stratigraphic  relations  of  the  Cambrian 
to  the  Ordovician  ? 

**7.  In  the  field,  where  would  you  look  for  the  continuation 
of  Cd,  after  its  interruption  in  the  southeast  part  of  the 
Dayton  Sheet  ? 

Absaroka  Folio  (Crandall  Sheet): 

1.  Note  the  position  of  the  beds. 

*2.  What  is  the  significance  of  the  distribution  of  Cambrian 
outcrops  ? 

3.  What  is  the  structure  which  gives  rise  to  the  arrange- 
ment of  outcrops  in  valleys  crossing  the  Cambrian  ? 
**4.  Why  do  not  the  Devonian  and  Carboniferous  strata 
show  on  the  lower  part  of  the  canyon  walls  down  stream  ? 

Tintic  Folio: 

1.  Study  the  structure  sections,  and  pp.  4  and  5  of  the  text 
of  the  folio. 

Clifton  Folio: 

1 .  With  what  systems  of  rocks  is  the  Cambrian  associated, 
and  what  are  its  relations  with  each  ? 

*2.  What  is  the  explanation  of  the  scattered  outcrops  of 
Cc  in  the  central  and  west  central  rectangles  ? 

*3.  Which  is  the  downthrow  side  of  the  fault  cutting  Cc, 
one  mile  north  of  Coronado  Mt.,  in  the  central  rectangle  ? 
**4.  Are  there  two  faults  or  three  1J  miles  south  of  Enebro 
Mountain  (north  central  rectangle)  ?     If  two,  is  the  earlier 
one  a  reversed  or  a  normal  fault?     Explain. 


42        STRUCTURAL  AND  HISTORICAL  GEOLOGY 

4.  General  Questions 

*1.  What  is  the  areal  distribution  of  the  outcrops  of  the 
system  as  shown  by  the  folios  ? 

*2.  State  the  general  character  of  the  rocks  of  the  system 
in  the  various  regions,  such  as  the  Appalachian  region,  the 
interior,  the  western  mountains,  etc.,  where  they  outcrop. 
**3.  What  is  the  position  (general  structure)  and  what  the 
condition  of  the  Cambrian  strata  and  of  associated  igneous 
rocks  (if  any)  in  the  several  regions  of  outcrop  ? 

*5.  Which  type  of  faulting  is  dominant  in  the  Tennessee 
region  ? 

**6.  What  are  the  economic  resources  of  the   Cambrian 
formations,  so  far  as  indicated  by  the  folios  ? 
**7.  Be  on  the  lookout  for  special  points  not  included  in  the 
above  general  questions.     Make  a  list  of  such  points. 

In  addition  to  the  folios  listed  in  the  exercise  above,  those 
named  below  also  show  outcrops  of  the  Cambrian  system.  In 
localities  where  the  Cambrian  system  occurs,  local  folios,  where 
they  exist,  may  be  substituted  for  some  of  those  listed  in  the 
exercise,  or  added  to  them. 

Anthracite-Crested  Butte,  Colo.  Mount  Mitchell,  N.  C. 

Cleveland,  Tenn.  Nantahala,  N.  C. 

Cloud  Peak-Fort  McKinney,  Wyo.  Penobscot  Bay,  Me. 

Cranberry,  N.  C.  Pikeville,  Tenn. 

Engineer  Mountain,  Colo.  Pawpaw-Hancock,  Md. 

Hawley,  Mass.  Rome,  Ga. 

Kingston,  Tenn.  Silverton,  Colo. 

Knoxville,  Tenn.  Staunton,  Va. 

Little  Belt  Mountains,  Mont.  Sundance,  Wyo. 

Livingston,  Mont.  Tenmile  District,  Colo. 

Loudon,  Tenn.  Trenton,  N.  J. 

Mine  La  Motte,  Mo.  Yellowstone,  Wyo. 


EXERCISE  IX 

ORDOVICIAN  AND  LATER  PALEOZOIC 

SYSTEMS 
I.  FOLIOS  TO  BE  STUDIED 

A.  Folios  for  Elementary  and  Briefer  Courses 


Aladdin,  Wyo. 
Bristol,  Va. 
Charleston,  W.  Va. 
Cloud   Peak-Fort    Me- 

Kinney,  Wyo. 
Colfax,  Cal. 
Danville,  111. 
Franklin  Furnace,  N.  J. 
Holyoke,  Mass. 
Joplin,  Mo. 

B.  Additional  Folios  for 
Absaroka,  Wyo. 
Bidwell  Bar,  Cal. 
Big  Trees,  Cal. 
Bisbee,  Ariz. 
Burgettstown-Carnegie, 

Pa. 

Claysville,  Pa. 
Downieville,  Cal. 
Fayetteville,  Ark. 
Gadsden,  Ala. 
Globe,  Ariz. 
Harpers  Ferry,  Va. 
Lassen  Peak,  Cal. 
Lancaster-Mineral 

Point,  Wis. 

43 


Latrobe,  Pa. 
Milwaukee,  Wis. 
Monterey,  Va. 
Morristown,  Tenn. 
Nevada  City,  Cal. 
Sundance,  Wyo. 
Walsenburg,  Colo. 
Warren,  Pa. 
Winslow,  Ark. 

More  Advanced  Students 
London,  Ky. 
Mother  Lode,  Cal. 
Needle  Mountains,  Colo. 
Oelrichs,  S.  D. 
Patoka,  Ind. 
Pawpaw-Hancock,  Md. 
Piedmont,  W.  Va. 
Pikeville,  Tenn. 
Pyramid  Peak,  Cal. 
Redding,  Cal. 
Rockland,  Me. 
Silverton,  Colo. 
Stevenson,  Ala. 
Tishomingo,  Ok.,  (I.  T.) 


44       STRUCTURAL  AND  HISTORICAL  GEOLOGY 

H.  OUTLINE  FOR  STUDY 
Note. — See  DIRECTIONS,  p.  35. 

1.   The  Interior  Region 
Danville  Folio: 

*1.  Explain  the  distribution  of  Carboniferous  outcrops. 
*2.  What  inference  can  be  made  from  the  outcrops  as  to 
the  position  of  the  Carboniferous  strata  ? 
*3.  Compare  the  elevation  of  the  upper  surface  of  the 
Carboniferous  at  the  heads  of  the  several  valleys.     Interpret. 
**4.  Could  there  be  more  than  one  explanation  for  the  dis- 
continuous   outcrops    of    Carboniferous    along    Vermilion 
River? 

5.  Study  the  columnar  sections  following  the  maps. 

Patoka  Folio: 

1.  Explain  the  general  distribution  of  the  Carboniferous 
outcrops. 

**2.  Account  for  the  failure  of  Cd  to  outcrop  between  Cs, 
and  Ci  on  certain  hill  slopes,  as  near  Erskine,  southwest 
part  of  the  map. 

Milwaukee  Folio: 

1.  Note  the  character  of  the  Paleozoic  rocks. 
**2.  What  is  the  explanation  of  the  isolated  outcrops  of 
Silurian  and  Devonian  rocks  scattered  over  the  area  ? 
**3.  Why  is  the  Devonian  confined  to  the  northeast  part  of 
the  region  ? 

Joplin  Folio: 

*1.  Why  do  so  few  formations  appear  in  this  region? 
**2.  Explain  the  fact  that  Cc  does  not  occur  under  Cck  in 
Sees,  14  and  23,  Twp,  28  N.,  R.  31  W.,  in  view  of  the  fact 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        45 

that  it  does  outcrop  just  south  of  here,  in  Sees.  23  and  26. 
Note  the  ages  of  the  beds  involved. 

Winslow  Folio: 

*1.  What  is  the  explanation  of  the  recurrence  of  beds  (as 
Chi)  in  the  valley  bottoms  ? 

2.  Can  an  unconformity  between  the  Mississippian  and 
the  Pennsylvanian  be  detected  on  the  map  ? 
**3.  At  Cove  Creek  in  the  west  central  part  of  the  map,  two 
faults  cross  each  other.  Is  it  possible  that  they  are  con- 
temporaneous ?  If  not,  what  can  be  concluded  as  to  the 
amount  of  dip  of  the  earlier  one  ? 

Tishomingo  Folio: 

**1.  Make  a  structure  section  from  Mill  Creek  (northwest 
part  of  map)  due  southwest  to  the  outcrop  of  Csa. 

Fayetteville  Folio: 

**1.  Explain  in  detail  the  distribution  of  Carboniferous  out- 
crops four  miles  east  of  Johnson,  in  the  northwest  part  of 
the  southeast  rectangle. 

**2.  Account  for  the  Devonian  outcrops  in  the  northern  part 
of  the  southwestern  rectangle. 

2.  Cumberland- Alleghany  Plateau  Region 

Charleston  Folio: 

*1.  What  is  the  general  structure  in  this  region? 
**2.  Explain  the  outcrops  of  Cs  in  certain  valleys  in  the 
south  central  rectangle. 

*3.  Explain  the  isolated  outcrops  of  Cbx  east  of  Charleston. 
4.  Study  the  relations  of  the  Lower  Carboniferous  to  the 
Carboniferous,  as  shown  on  the  Columnar  Section  Sheet. 


46       STRUCTURAL  AND  HISTORICAL  GEOLOGY 

Latrobe  Folio: 

1.  Study    in    detail    the    outcrops    along    the    line    of 
Chestnut  Ridge. 

2.  What  is  the  meaning  of  the  Cm  patches  within  Ccm, 
northwest  central  part  of 'map? 

3.  What  is  the  meaning  of  the  Ccs  outcrop  within  Ccm 
to  the  east  of  Nihil  in  the  northwest  part  of  the  map  ? 

3.   The  Appalachian  Region 

Warren  Folio: 

1.  Note    the    general    character    and    structure    of    the 
Paleozoic  strata. 

2.  Notice  especially  the  texture  of  the  Carboniferous  beds. 
**3.  a)  Account  for  the  juxtaposition  of  Cpo  and  Ck  at 
several  points  in  the  east  central  part  of  the  area. 

b)  Determine  the  thickness  of  Cch  in  the  eastern  part 
of  the  sheet. 

c)  What  is  the  minimum  amount  of  post-Mississippian 
pre-Pennsylvanian  erosion  ? 

d)  Give  some  idea  of  the  time  represented  by  this 
unconformity. 

*4.  Explain  the  failure  of  Cps  and  Cpo  to  appear  between 
Cch  and  Cpc  in  the  east  central  part  of  the  area.  Take 
into  consideration  the  lithological  character  of  the  formations 
involved. 

Monterey  Folio: 

**1.    Has    folding   or   faulting   been  the  more   important 
factor  in  determining  the  arrangement  of  outcrops  ? 
**2.  Explain  the  isolated  outcrops  of  Cpo  in  the  north 
central  rectangle. 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        47 

*3.  What  striking  difference  is  there  between  the  structure 
of  this  region  and  that  of  the  Morristown  quadrangle  ? 

*4.  Explain  the  concentric  arrangement  of  outcrops  with 
Sj  in  the  center,  near  the  eastern  border  of  the  south  central 
rectangle. 

*5.  From  the  data  given  on  the  map,  what  inference  can 
be  drawn  concerning  the  age  of  the  igneous  outcrops  in  the 
northeast  rectangle? 

6.  Is  there  more  than  one  possible  explanation  for  the 
distribution  of  igneous  outcrops  shown  in  the  northeast 
rectangle  ? 

7.  Note  the  structural  positions  of  the  valleys  in   the 
different  parts  of  the  map. 

8.  What  is  the  structure  of  the  high  points  ? 

Bristol  Folio: 

1.  Compare  the  attitude  of  the  Silurian  and  Devonian 
beds  with  that  of  the  Carboniferous  beds. 
**2.  Explain  the  distribution  of  the  outcrops  of  Sa  in  the 
southeast  portion  of  the  map. 

**3.  Study  the  contact  of  the  Carboniferous,  in  the  north- 
west part  of  the  map,  with  the  formations  to  the  southeast. 
Follow  this  contact  across  the  sheet,  and  determine  the 
structure  which  occasions  the  various  outcrops. 

*4.  Explain  the  isolated  patches  of  Cnr  and  Cws  in  the 
northwest  corner  of  the  map. 

**5.  Explain  the  distribution  of  the  Devonian  outcrops,  DC 
and  Dcg. 

*6.  Why  is  there  so  little  Devonian  at  the  surface  ? 

*7.  Why  are  the  outcrops  of  Devonian  narrower  here  than 
in  the  Monterey  region  ? 


48       STRUCTURAL  AND  HISTORICAL  GEOLOGY 

8.  Why  are  there  no  Carboniferous  outcrops  in  the  south- 
east part  of  the  area  ? 

9.  What  is  the  meaning  of  the  outcrop  marked  SDh, 
through  the  central  portion  of  the  map  ? 

10.  Determine  the  downthrow  side  of  the  faults  just  west 
of  Ravens  Nest,  central  rectangle. 

11.  Note  the  relation  of  drainage  to  structure. 

Franklin  Furnace  Folio: 

*1.  Explain  the  interruption  of  Oj,  1^  miles  north  of 
Lafayette,  in  the  west  central  rectangle. 

*2.  Explain  the  offset  in  Oj  in  the  north  central  part  of 
the  central  rectangle.  How  does  this  differ  from  the  fault 
in  1? 

**3.  Work  out  the  history  of  the  Ordovician  outcrops  in 
the  northwest  part  of  the  west  central  rectangle. 

4.   The  New  England  Region 

Holyoke  Folio: 

1.  What  general  structure  is  suggested  by  the  arrange- 
ment of  outcrops  in  the  southwest  rectangle  ? 

*2.  Explain  the  form  of  the  Sg  outcrop  in  the  west  central 
rectangle,  including  the  peculiarity  of  outcrop  at  the 
westernmost  crossing  of  the  Westfield  River. 
**3.  How  would  you  go  to  work  in  the  field  to  determine 
the  age  of  the  Cw  formation  ?  Designate  the  most  important 
or  most  favorable  places  to  visit. 

**4.  What  possible  explanations  can  be  given,  from  a  study 
of  the  Historical  Geology  Sheet,  for  the  present  distribu- 
tion of  Cw  outcrops  ? 

**5.  How  would  you  go  to  work  in  the  field  to  determine 
whether  Cw  is  intrusive  or  extrusive  ? 


STRUCTURAL  AND  HISTORICAL  GEOLOGY       49 

*6.  Account  for  the  outcrop  of  Sg  in  the  north  central  and 
northwestern  rectangles. 

5.  East  Base  of  Rocky  Mountains 

Walsenburg  Folio: 

This  may  be  regarded  as  a  type  of  the  Carboniferous  out- 
crops at  the  east  base  of  the  Rocky  Mountains.  Study  its 
general  features. 

Aladdin  Folio: 

1.  What  feature  occasions  the  intricate  outcrops  in  the 
southwest  corner  of  the  sheet  ? 

*2.  From  the  Areal  Geology  Sheet,  determine  the  nature  of 
the  chief  feature  at  Sheep  Mtn.  Test  your  conclusion  by 
the  structure  section  sheet. 

Sundance  Folio: 

*1.  What  is  the  structure  of  Bear  Lodge  Mountains  in  the 
northwest  corner  of  the  area  ? 

**2.  What  data  were  used  in  mapping  Green  Mtn.,  Bald 
Mtn.,  and  Strawberry  Mtn.  as  laccoliths  on  the  structure 
section  sheet  ? 

3.  From  the  structure  section  sheet,  what  can  be  said  of 
the  date  of  vulcanism  north  of  Cement  Ridge  ? 

6.   The  Rocky  Mountain  Region 

Absaroka  Folio  (Crandall Sheet): 

**1.  What  are  the  possible  ways  of  explaining  the  present 
arrangement  of  Devonian  and  Carboniferous  outcrops? 
Study  especially  in  this  connection  the  Sunlight  Basin  in 
the  east  central  rectangle.  Why  does  not  Cambrian  appear 
in  this  rectangle  ? 


50       STRUCTURAL  AND  HISTORICAL  GEOLOGY 

**2.  Work  out  the  physical  history  of  the  region  where  the 
Carboniferous  and  Devonian  appear. 

Cloud  Peak-Fort  McKinney  Folio: 

*1.  What  is  the  date  of  the  faulting  at  Bald  Ridge,  just 
west  of  the  Fort  McKinney  Military  Reservation  ? 
**2.  Explain  the  failure  of  the  Paleozoics  to  outcrop  along 
the  Archean  in  two  places  northwest  of  Buffalo. 

Needle  Mountains  Folio: 

**1.  Work  out  the  sequence  of  the  faulting  in  the  northeast 
corner  of  the  northwest  rectangle.  On  the  basis  of  but  three 
faults,  is  the  first  one  reversed  or  normal  ? 

Silverton  Folio: 

**1.  Work  out  the  physical  history  of  this  region  to  the  close 
of  the  Paleozoic. 

7.   The  Arizona  Region 

Globe  Folio: 

**1.  Make  a  structure  section  from  the  letter  "B"  in  the 
name  "Granite  Basin"  (northwestern  part  of  map),  north- 
east to  the  letter  "B"  in  the  name  "Ruin  Basin." 

2.  Work  out  the  structure  along  the  section  line  AA  from 
the  Areal  Geology  Sheet,  and  then  compare  it  with  the 
structure  section. 

Bisbee  Folio: 

1.  Work  out  in  as  great  detail  as  possible  the  history  of  the 
faulted  area  about  Bisbee.  The  fault-diagram  sheet  will 
be  helpful. 

**2.  Study  the  structure  sections  and  interpret  the  physical 
history  of  the  region. 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        51 

8.   The  California  Region 
Coif  ax  Folio: 

**1.  What  has  been  the  chief  factor  in  determining  the 
present  form  and  distribution  of  Carboniferous  outcrops? 
Note  their  topographic  position. 

2.  From  the  structure  sections,  notice  the  various  forma- 
tions with  which  the  Carboniferous  comes  in  contact. 

*3.  What  was  the  character  of  the  topography  of  the  region 
at  the  time  of  the  Na  flows  ? 

Nevada  City  Special  Folio: 

Note  the  scale,  contour  interval,  and  great  detail  of  this 
map. 

*1.  How  may  the  present  outcrops  of  Carboniferous  be 
accounted  for  ? 

2.  From  the  sections,  determine  with  what  formations  the 
Carboniferous  comes  in  contact  in  this  region. 

3.  What  is  the  condition  of  the  Carboniferous  rocks  in  this 
region  ? 

**4.  From  the  structure  sections,  can  any  generalization  be 
made  as  to  the  location  of  the  ore  veins  ? 

5.  Note  the  location  of  the  auriferous  gravels  and  their 
positions  relative  to  the  present  drainage  lines. 

General  Questions  on  the  California  Region 

**1.  What  is  the  general  geographic  location  of  the  areas 

shown  on  the  folios  ? 

**2.  Which  of  the  several  Paleozoic  systems  appear  in  this 

region  ? 

**3.  What  is  the  condition  of  the  Paleozoic  formations  in 

this  region  ? 


52        STRUCTURAL  AND  HISTORICAL  GEOLOGY 

**4.  With  what  other  systems  do  the  Paleozoic  beds  come 
in  contact  ? 

**5.  How,  in  general,  may  the  present  outcrops  of  Paleozoic 
rocks  be  accounted  for  ? 

6.  Note  the  contacts  of  the  Carboniferous  in  the  Pyramid 
Peak  folio. 

General  Questions  on  the  Ordovician,  Silurian,  Devonian,  and 
Carboniferous  Systems 

I.  Compare  the  positions  of  the  Ordovician,  Silurian, 
Devonian  and  Carboniferous  strata  in  the  different  regions. 
**2.  What  changes  in  structure  occur  in  passing  from  north 
to  south  in  the  Appalachians  ? 

*3.  Compare  the  relative  areas  of  outcrop  of  the  Silurian, 
Devonian,  and  Carboniferous  formations  in  each  region. 

4.  What   are   the   relative   thicknesses   of   the   Silurian, 
Devonian,  and  Carboniferous  formations  in  each  region  ? 
**5.  What   structure   prevails    at   the   west   or   northwest 
border  of  the  Appalachian  Mountain  belt  ? 
**6.  Compare  the  outcrops  of  Devonian  in  Maryland  and 
West  Virginia  with  those  in  eastern  Tennessee  and  Alabama. 

*7.  Does  the  same  type  of  faulting  prevail  in  all  parts  of 
the  Appalachian  Mountains  ?  Note  the  location  as  well  as 
the  fact  of  variations,  if  such  occur. 

*8.  Where  is  faulting  and  where  is  folding  the  more 
important  ? 

**9.  What  are  the  ages  of  the  igneous  rocks  associated  with 
the  Paleozoic  strata  in  the  various  regions  ? 

*10.  In  which  region  has  vulcanism  most  affected  the 
Paleozoic  systems  ? 

II.  What  kinds  of  rock  represent  the  different  Paleozoic 
periods  in  the  various  regions  ? 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        53 


The  folios  listed  below  also  show  outcrops  of  the  later  Paleozoic 
systems,  and  they  may  be  used,  if  a  more  extended  course  is  desired; 
or,  folios  of  local  interest  may  be  substituted  for  some  of  those 
listed  above,  or  added  to  them. 


Amity,  Pa. 

Anthracite— Crested  Butte,  Colo. 

Asheville,  N.  C. 

Atoka,  Ok.  (I.  T.) 

Bald  Mountain-Dayton,  Wyo. 

Beaver,  Pa. 

Briceville,  Tenn. 

Brownsville-Connelsville,  Pa. 

Buckhannon,  W.  Va. 

Chattanooga,  Tenn. 

Chicago,  111. 

Cleveland,  Tenn. 

Clifton,  Ariz. 

Coalgate,  Ok.  (I.  T.) 

Columbia,  Tenn. 

Cottonwood  Falls,  Kas. 

Ditney,  Ind. 

Ebensburg,  Pa. 

Edgemont,  S.  D. 

Elders  Ridge,  Pa. 

Elkland-Tioga,  Pa. 

El  Paso,  Texas. 

Estillville,  Ky. 

Foxburg-Clarion,  Pa. 

Fort  Benton,  Mont. 

Franklin,  W.  Va. 

Gaines,  Pa. 

Greeneville,  Tenn. 

Hartville,  Wyo. 

Hawley,  Mass. 

Huntington,  W.  Va. 

Independence,  Kas. 

Indiana,  Pa. 

Jackson,  Cal. 


Johnstown,  Pa. 
Kingston,  Tenn. 
Kittanning,  Pa. 
Knoxville,  Tenn. 
Laramie-Sherman,  Wyo. 
Little  Belt  Mountains,  Mont. 
Livingston,  Mont. 
Loudon,  Tenn. 
Masontown-Uniontown,  Pa. 
Maynardville,  Tenn. 
McMinville,  Tenn. 
Mercersburg-Chambersburg, 

Pa. 

Mount  Stuart,  Wash. 
Muskogee,  Ok.  (I.  T.) 
Newcastle,  Wyo. 
New  York  City,  N.  Y. 
Ouray,  Colo. 
Passaic,  N.  J. 
Pocahontas,  Va. 
Penobscot  Bay,  Me. 
Pikes  Peak,  Colo. 
Placerville,  Cal. 
Raleigh,  W.  Va. 
Richmond,  Ky. 
Rico,  Colo. 
Ringgold,  Ga. 
Rogersville,  Pa. 
Rome,  Ga. 
Rural  Valley,  Pa. 
Sacramento,  Cal. 
Sewanee,  Tenn. 
Sewickley,  Pa. 
Smartsville,  Cal, 


54        STRUCTURAL  AND  HISTORICAL  GEOLOGY 

Snoqualmie,  Wash.  Three  Forks,  Mont. 

Sonora,  Cal.  Tintic,  Utah. 

Standingstone,  Tenn.  Wartburg,  Tenn. 

Staunton,  Va.  Watkins  Glen-Catatonk,  N.  Y. 

Tahlequah,  Ok.  (I.  T.)  Waynesburg,  Pa. 

TazeweU,  Va.  Yellowstone,  Wyo. 

Tenmile  District,  Colo. 


EXERCISE  X 

TRIASSIC  AND  JURASSIC 
I.  FOLIOS  TO  BE  STUDIED 

A.  Folios  for  More  Elementary  and  Briefer  Courses 
Belle  Fourche,  S.  D.  Philadelphia,  Pa. 
Holyoke,  Mass.  Pyramid  Peak,  Cal. 
Laramie-Sherman,  Wyo.  Roseburg,  Ore. 
Ouray,  Colo.  Tenmile  District,  Colo. 
Passaic,  N.  J.  Trenton,  N.  J. 

B.  Additional  F olios  for  More  Advanced  Courses 
Aladdin,  Wyo.  Harpers  Ferry,  Va. 
Bald  Mountain-Dayton,    Mother  Lode,  Cal. 

Wyo.  Mount  Mitchell,  N.  C. 

Colfax,  Cal.  Redding,  Cal. 

Cranberry,  N.  C.  Rico,  Colo. 

Devils  Tower,  Wyo.  Sonora,  Cal. 

Edgemont,  S.  D.  Telluride,  Colo. 
Engineer  Mountain,  Colo.  Truckee,  Cal. 
Fort  Benton,  Mont. 

II.  OUTLINE  FOR  STUDY 

Note. — See  DIRECTIONS,  p.  35,  and  Note,  p.  11. 

1.  Eastern  United  States 
Holyoke  Folio: 

1.  Can  the  existence  of  a  fault  along  the  west  margin  of 
the  Jura-Trias  be  determined  from  the  Historical  Geology 
Sheet?  See  the  Structure  Section  Sheet, 

55 


56        STRUCTURAL  AND  HISTORICAL  GEOLOGY 

2.  Note  the  various  sorts  of  igneous  rocks  associated  with 
the  Jura-Trias. 

**3.  What  inference  can  be  drawn  from  the  shape  of  the 
outcrop  of  the  Holyoke  diabase?  Carry  this  inference  to 
details. 

*4.  How  might  it  be  determined  in  the  field  whether  or  not 
the  two  southern  exposures  of  Jhp  (east  part  of  south  central 
rectangle)  are  parts  of  the  same  lava  bed  ? 
**5.  a)  Can  it  be  told  from  the  Historical  Geology  Sheet 
whether  Jhp  in  the  south  central  rectangle  is  a  dike,  or  an 
interbedded  lava  sheet  ? 

b)  How  might  it  be  determined  in  the  field  ? 

c)  If  Jhp  is  a  sheet,  how  may  it  be  determined  whether 
it  was  intrusive  or  extrusive? 

6.  The  relative  age  of  Jhp  and  Jb,  in  the  east  central 
rectangle  ? 

7.  Study  the  relations  of  the  various  sorts  of  igneous  rocks 
to  one  another,  and  to  the  sedimentary  rocks,  as  shown  by 
the  Structure  Section  Sheet. 

Passaic  Folio: 

1.  Note  the  geographic  and  physiographic  location  of  this 
area. 

2.  Note  the  contact  of  the  Triassic  with  older  rocks  in 
the  northwest  part  of  the  area. 

*3.  How  would  you  determine  in  the  field  whether  or  not 
the  contact  of  the  Triassic  with  older  rocks  is  a  fault  contact  ? 

4.  How  have  the  igneous  outcrops  influenced  the  topog- 
raphy of  the  region  ? 
**5.  Explain  the  hooked  outcrops  of  Trw. 

6.  The  age  of  Trw  and  Trp  ? 
**7.  a)  Can  it  be  told  from  the  Areal  Geology  map  whether 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        57 

Trw,  is  in  the  form  of  dikes  or  interbedded  lava  sheets  ? 

b)  How  might  it  be  determined  in  the  field  ? 

c)  If  Trw  is  a  sheet,  how  may  it  be  determined  whether 
it  was  intrusive  or  extrusive. 

Trenton  Folio: 

1.  Note  (a)  the  character  of  the  Triassic  igneous  rocks, 
and  (b)  their  relation  to  the  sedimentary  rocks. 

*2.  Does  the  areal  geology  sheet  (including  legend)  show 
whether  the  igneous  rocks  were  intrusive  or  extrusive?  If 
so,  how? 

3.  Note   the  influence   of  the   several   members   of  the 
Triassic  system  on  the  topography. 

Philadelphia  Folio: 

*1.  Account  for  the  juxtaposition  of  Trs  with  older  beds 
of  varying  ages  on  the  Norristown  and  Germantown  sheets. 

2.  Explain  the  isolated  outcrops  of  Trs  in  the  southwest 
corner  of  the  central  rectangle,  Norristown  sheet. 

**3.  How  did  the  author  of  the  folio  know  that  the  diabase 
dikes  were  Triassic  ? 

2.   The  Western  Interior  Region 
Belle  Fourche  Folio: 

1.  Note  the  location  of  this  quadrangle  with  reference  to 
the  Black  Hills  uplift. 

*2.  Work  out  the  early  Mesozoic  history  of  the  quadrangle 
from  the  lithologic  characteristics  and  the  structural  and 
stratigraphic  relations  of  the  Spearfish  and  Sundance 
formations. 

Tenmile  Folio: 
*1.  What  structure  could  give  rise  to  the  peculiar  relation 


58        STRUCTURAL  AND  HISTORICAL  GEOLOGY 

of  sedimentary  and  igneous  rock  outcrops  shown  on  the 
economic  geology  sheet  ? 

2.  Study  the  two  Structure  Section  sheets. 

3.  Do  the  structure  sections  afford  the  data  necessary  for 
determining    whether    the    igneous    rock    is    intrusive    or 
extrusive  ? 

3.   The  Rocky  Mountain  Region 

Our  ay  Folio: 

1.  Notice  the  stratigraphic  and  structural  relations  of  the 
Triassic  and  Jurassic  formations. 

**2.  Draw  a  structure  section  from  Baldy  Peak,  in  the  west 
central  rectangle,  southwest  to  the  edge  of  the  sheet. 

*3.  Determine  the  age  of  the  east-west  fault  immediately 
south  of  Ouray. 

**4.  Interpret  the  relation  of  Tqm  to  the  early  Mesozoic 
formations,  southwest  of  Ouray. 

Rico  Folio: 

1.  What  inference  concerning  the  structure  may  be 
drawn  from  the  arrangement  of  the  Triassic  and  Jurassic 
formations  ? 

**2.  Give  the  physical  history  of  this  region  during  the  early 
Mesozoic  time. 

**3.  Is  the  Thm,  near  the  south  border  of  the  quadrangle, 
intrusive  or  extrusive  ?     Reasons  for  your  answer  ? 

Laramie-Sherman  Folio: 
1.  Note  the  location  of  the  area. 

*2.  Explain  the  absence  of  the  Sundance  formation  in  the 
Laramie  quadrangle,  and  its  presence  in  the  Sherman 
quadrangle. 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        59 

*3.  a)  What  field  evidence  would  you  use  to  prove  the 
presence  or  absence  of  Permian  in  the  Chugwater  formation  ? 

b)  If  the  lower  Chugwater  beds  are  of  Permian  age, 
what  are  the  stratigraphic  relations  of  the  Permian  beds  of 
the  region  ? 

c)  Judging  from  this  folio,  would  the  Permian  better 
be  classed  with  the  Paleozoic  or  the  Mesozoic  ? 

Fort  Benton  Folio: 

1.  How  are  the  peculiar  outcrops  of  Je  in  the  southeastern 
part  of  the  map,  at  Skull  Butte  and  southwest  of  Skull 
Butte,  to  be  interpreted  ? 

4.   The  Pacific  Coast 

Pyramid  Peak  Folio: 

Study  the  structure  sections  and  compare  them  with  the 
Areal  Geology  Sheet,  especially  for  the  relation  of  igneous 
rock  to  the  Jura-Trias.  (The  Mother  Lode,  Colfax,  and 
Sonora,  Cal.,  folios  show  similar  conditions.) 

Redding  Folio: 

**1.  Work  out  the  early  Mesozoic  history  of  the  region  from 
a  study  of  the  relations  of  the  beds  and  their  lithology. 

2.  Explain  the  peculiar  shape  of  the  Trh  outcrops  in  the 
east  central  and  northeast  rectangles. 

Roseburg  Folio: 

1.  Note  the  relations  of  the  Jr  outcrops  to  the  other  forma- 
tions in  the  southwest  rectangle.  The  possible  interpreta- 
tion of  these  outcrops  ? 

5.  General  Questions  on  the  Triassic  and  Jurassic 

(Jura-  Trias) 

**1.  Compare  the  structural  conditions  of  the  Jura-Trias 
strata  in  the  different  regions. 


60       STRUCTURAL  AND  HISTORICAL  GEOLOGY 

*2.  Compare  the  structure  of  the  Jura-Trias  of  the  East 
with  the  structure  of  the  Paleozoic  of  the  Appalachians. 

*3.  Compare  the  structure  of  the  Jura-Trias  of  the  West 
with  that  of  the  Paleozoic  of  the  West. 

**4.  What  are  the  different  factors  determining  the  forms  of 
the  outcrops  in  the  various  regions  ? 

*5.  What  kinds  of  rocks  represent  the  Jura-Trias  in  the 
different  regions  ? 

**6.  What  kinds  of  rocks  have  resulted  from  contact  meta- 
morphism  ? 

7.  To  what  distances,  as  shown  on  the  maps,  has  contact 
metamorphism  affected  the  clastic  formations  ? 
**8.  What  economic  products  are  found  in  or  associated 
with  the  Jura-Trias  formations,  in  the  areas  represented  by 
the  folios  ? 

**9.  The  relations  of  the  Jura -Trias  sedimentary  beds  to 
igneous  rocks. 

a)  In  the  East. 

b)  In  the  West. 

The  following  folios  may  be  used  for  a  more  extended  study  of 

the  Triassic  and  Jurassic  systems,  or  for  substitution  in  the  list 
given  in  the  exercise  above: 

Anthracite-Crested  Butte,  Colo.  New  York  City,  N.  Y. 

Bidwell  Bar,  Cal.  Oelrichs,  S.  D. 

Cloud  Peak-Fort  McKinney,  Wyo.  Patuxent,  Md. 

Downieville,  Cal.     .  Pikes  Peak,  Colo. 

Hartville,  Wyo.  Pisgah,  N.  C. 

Jackson,  Cal.  Pueblo,  Colo. 

La  Plata,  Colo.  San  Luis,  Cal. 

Lassen  Peak,  Cal.  Santa  Cruz,  Cal. 

Little  Belt  Mountains,  Mont.  Three  Forks,  Mont. 

Marysville,  Cal.  Walsenburg,  Colo. 

Monterey,  Va.  Yellowstone,  Wyo. 

Newcastle,  Wyo. 


EXERCISE  XI 

COMANCHEAN  AND  CRETACEOUS 
I.  FOLIOS  TO  BE  STUDIED 

1.   The  Atlantic  Coast 
Dover,  Del.  Patuxent,  Md. 

Fredericksburg,  Va.  Trenton,  N.  J. 

Passaic,  N.  J.  Washington,  D.  C. 

2.   Texas 

Austin  Nueces 

El  Paso  Uvalde 

3.   The  Great  Plains 

Aberdeen-Redfield,  S.  D.    Jamestown-Tower,  N.  D. 
Aladdin,  Wyo.  Laramie-Sherman,  Wyo. 

Belle  Fourche,  S.  D.  Olivet,  S.  D. 

Bismarck,  N.  D.  Parker,  S.  D. 

Devils  Tower,  Wyo.  Sundance,  Wyo. 

4.   The  Rocky  Mountains 

Bald  Mountain-Dayton,  Little  Belt  Mountains, 

Wyo.  Mont. 

Cloud   Peak-Fort    Me-  Rico,  Colo. 

Kinney,  Wyo.  Spanish  Peaks,  Colo. 

Elmoro,  Colo.  Telluride,  Colo. 
Engineer  Mountain,  Colo. 

5.   The  Pacific  Coast 

Coif  ax,  Cal.  Lassen  Peak,  Cal. 

Coos  Bay,  Ore.  Roseburg,  Ore. 

61 


62       STRUCTURAL  AND  HISTORICAL  GEOLOGY 
II.  DIRECTIONS 

Elementary  and  Briefer  Courses. — Study  enough  of  the 
folios  of  each  region  listed  above  to  enable  you  to  answer  the 
questions  marked  *,  in  the  outline  below. 

Advanced  Courses. — Study  all  the  folios  listed  above,  and 
answer  in  writing  questions  marked  *  and  **.  Study  the 
texts  as  well  as  the  maps  of  the  folios,  wherever  it  is  necessary 
to  answer  the  questions  fully. 

Note.— See  Note,  p.  11. 

HI.  QUESTIONS 

*1.  What  are  the  stratigraphic  relations  of  the  Cretaceous 
beds  to  the  overlying  and  underlying  formations  in  the 
different  regions,  so  far  as  shown  in  the  folios  ? 
**2.  Prepare  diagrams  illustrating  the  structural  conditions 
of  the  Cretaceous  and  associated  strata  in  the  different 
regions. 

*3.  What  are  the  factors  determining  the  general  forms  of 
the  outcrops  of  Cretaceous  in  the  different  regions  ? 

*4.  Prepare  one  large  diagram,  or  a  series  of  smaller 
diagrams,  illustrating  all  the  ways  in  which  igneous  rock  is 
associated  with  the  Cretaceous. 

**5.  What  is  the  age  of  the  igneous  rock  associated  with  the 
Cretaceous  in  the  different  regions,  and  how  is  this  age 
determined  ? 

*6.  What  kinds  of  rock  represent  the  Cretaceous  system  in 
the  different  regions  ? 

**7.  What,  if  any,  products  of  economic  value  do  the  Creta- 
ceous formations  contain,  as  shown  in  the  folio  maps  ? 

*8.  Determine  as  closely  as  possible  from  the  folios,  the 
date  of  origin  of  the  Rocky  Mountains.  Read  especially  in 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        63 


this  connection  the  description  of  the  Kingsbury  conglom- 
erate, p.  8,  Bald  Mountain- Day  ton  folio. 

The  following  folios  may  also  be  used  to  illustrate  the  Coman- 
chean  and  Cretaceous  systems: 
Alexandria,  S.  D. 
Anthracite-Crested  Butte,  Colo. 
Atoka,  Ok.  (I.  T.) 
Edgemont,  S.  D. 
Elk  Point,  S.  D. 
Fort  Benton,  Mont. 
Hartville,  Wyo. 
La  Plata,  Colo. 
Livingston,  Mont. 
Mitchell,  S.  D. 
Mother  Lode,  Cal. 
Nepesta,  Col. 
Newcastle,  Wyo. 
New  York  City,  N.  Y. 
Oelrichs,  S.  D. 


Ouray,  Colo. 
Philadelphia,  Pa. 
Pikes  Peak,  Colo. 
Placerville,  Cal. 
Port  Orford,  Ore. 
Pueblo,  Colo. 
Redding,  Cal. 
San  Luis,  Cal. 
Santa  Cruz,  Cal. 
Tishomingo,  Ok.  (I.  T.) 
Three  Forks,  Mont. 
Truckee,  Cal.   ' 
Walsenburg,  Colo. 
Yellowstone,  Wyo. 


EXERCISE  XII 
TERTIARY 
I.  FOLIOS  TO  BE  STUDIED 

A.  Folios  for  More  Elementary  and  Briefer  Courses 
Aladdin,  Wyo.  Needle  Mountains,  Colo, 
Bald  Mountain- Dayton,          Ouray,  Colo. 

Wyo.  Patuxent,  Md. 

Bismarck,  N.  D.  Philadelphia,  Pa. 

Bradshaw  Mountains,  Ariz.  Rico,  Colo. 

Choptank,  Md.  Snoqualmie,  Wash. 
Cloud  Peak-Fort  McKinney,  St.  Marys,  Md. 

Wyo.  Sundance,  Wyo. 

Devils  Tower,  Wyo.  Trenton,  N.  J. 
Dover,  Del. 

B.  Additional  Folios  for  More  Advanced  Courses 
Absaroka,  Wyo.  Nevada  City,  Cal. 
Big  Trees,  Cal.  Nomini,  Md. 
Boise,  Idaho.  Richmond,  Ky. 
Coif  ax,  Cal.  Roseburg,  Ore. 
Coos  Bay,  Ore.  San  Luis,  Cal. 
Downieville,  Cal.  Santa  Cruz,  Cal. 
Elk  Point,  S.  D.  Tacoma,  Wash. 
Little  Belt  Mountains,  Walsenburg,  Colo. 

Mont.  Washington,  D.  C. 

Mother  Lode,  Cal. 

64 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        65 

H.  DIRECTIONS 

Elementary  Course. — Study  the  folios  of  Group  A  above. 
Omit  the  General  Questions.  Prepare  answers  to  all  ques- 
tions except  those  marked  **,  and  answer  in  writing  ques- 
tions marked  *. 

Advanced  Course. — Study  all  the  folios  of  A  and  B  above, 
using  those  of  Group  B  especially  for  answering  the  General 
Questions.  The  folios  should  be  studied  with  particular 
care,  the  structure  sections  and  texts  being  used  freely. 
Answer  in  writing  questions  marked  *  and  **. 

Note.— See  Note,  p.  11. 

m.  QUESTIONS 

1.   The  Atlantic  Coast 

Patuxent,  St.  Marys,  Dover,  Philadelphia,  Choptank,  and 
Trenton  Folios: 

*1.  What  conclusions  concerning  the  physical  geography 
of  the  Eocene  period  can  be  drawn  from  the  character  of 
the  Eocene  rocks  ? 

**2.  State  the  history  of  the  Tertiary  in  the  region  from  the 
description  of  the  Tertiary  system.  For  details,  read  the 
sections  on  Historical  Geology  in  the  folios. 

2.  Black  Hills  and  Great  Plains 

Aladdin,  Devils  Tower,  Sundance,  and  Bismarck  Folios: 
*1.  What  was  the  date  of  deformation  of  the  Black  Hills? 
Reasons. 
**2.  The  relative  ages  of  deformation  and  igneous  activity  ? 

3.  What  forms  were  taken  by  the  igneous  rocks  ? 
*4.  Give  in  detail  the  events  that  led  up  to  the  formation 
of  Devils  Tower  (Devils  Tower  folio). 
5 


66       STRUCTURAL  AND  HISTORICAL  GEOLOGY 

5.  Elk  Point  Folio: 

**a)  Is   there  any  suggestion  of  a  more  extensive    distri- 
bution of  the  Tertiary  than  is  shown  on  the  map  ? 
**b)  What  would  be  the  basis  for  conclusions  concerning 
such  changes  of  drainage  as  those  described  in  the  History 
of  the  Tertiary  ?     (See  text  of  folio.) 

3.   The  Bighorn  Mountains 

Cloud  Peak— Fort  McKinney  and  Bald  Mountain-Dayton 
Folios: 

*1.  From  the  geologic  map,  determine  as  closely  as  may 
be  the  age  of  the  Bighorn  Mountains. 

2.  Read  the  descriptions  of  the  Tertiary  formations  in  the 
texts  of  the  folios,  noting: 

a)  The  character  of  the  beds. 

b)  Their  topographic  position. 

c)  Their  stratigraphic  relations. 

**d)  Read  "Age  and  Origin,"  p.  9,  Cloud  Peak-Fort 
McKinney  Folio.  What,  would  you  say  of  the  probability 
of  the  glacial  origin  of  these  beds  ? 

4.   The  San  Juan  Mountains 
Needle  Mountains,  Ouray,  and  Rico  Folios: 
**1.  Name    the   chief    events  of    the  Tertiary  period  in 
chronological  order. 

**2.  What  is  the  relation  of  the  deformation  to  the  ore 
deposits  ?     Which  epoch  of  deformation  is  involved  ? 

*3.  From  the  Rico  Areal  Geology  Sheet,  determine  the 
relative  ages  of  the  igneous  activity  and  the  faulting. 

4.  Compare  the  San  Juan  uplift  with  the  main  area  of 
the  Rocky  Mountains,  as  to 

a)  Character  of  deformation. 

b)  Date  of  deformation, 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        67 

*5.  What  are  the  stratigraphic  relations  of  the  Telluride 
conglomerate  ? 

5.   The  Cascade  Mountains 

Snoqualmie  Folio: 

**1.  Describe  the  geographic  conditions  of  the  early  Eocene. 
*2.  What  was  the  chief  event  of  the  Tertiary  period  ? 

6.  Arizona 

Bradshaw  Mountains  Folio: 

*1.  Of  what  rocks  is  the  Tertiary  system  composed? 
**2.  How  were  the  ores  deposited  ? 
3.  The  age  of  the  ores  ? 

7.   The  Coast  Ranges 

Santa  Cruz  Folio: 

**1.  List  the  principal  events  of  this  region  during  the 
Tertiary  period.  Include  geographic  changes,  diastrophic 
events,  and  igneous  activity. 

8.  General  Questions  on  the  Tertiary 

**1.  Adapt  the  general  questions  on  the  Cretaceous  (p.  62), 
to  the  Tertiary  formations,  noting  the  following: 

a)  Study  in  detail  (reading  text)  the  Nomini,  Washing- 
ton, Richmond,  Tacoma,  and  San  Luis  folios. 

b)  In  connection  with  the  stratigraphic  relations  of  the 
Tertiary  beds,  study  the  columnar  sections  in  the  more 
recent  folios. 

c)  In  connection  with  the  igneous  rocks  associated 
with  the  stratified  Tertiary  formations,  study  particularly 
the    following    folios:     Ouray    and    Walsenburg,     Colo., 
Absaroka,  Aladdin,  Devils  Tower,  and  Sundance,  Wyo., 


68        STRUCTURAL  AND  HISTORICAL  GEOLOGY 


Little  Belt,  Mont.,  Bradshaw  Mountain,  Ariz.,  Boise, 
Idaho.,  Big  Trees,  Nevada  City,  Santa  Cruz,  Colfax, 
Downieville,  Mother  Lode,  Cal.,  and  Roseburg  and  Coos 
Bay,  Ore. 

In  addition  to  the  maps  listed  above,  the  following  folios  also 
show  Tertiary  formations,  and  should  be  used  if  more  extended 
study  is  desired: 

Anthracite-Crested  Butte,  Colo. 


Austin,  Texas. 
Bidwell  Bar,  Cal. 
Butte  Special,  Mont. 
Camp  Clarke,  Neb. 
Coalgate,  Ok.  (I.  T.) 
Edgemont,  S.  D. 
Ellensburg,  Wash. 
Elmoro,  Colo. 
Fort  Benton,  Mont. 
Fredericksburg,  Va. 
Globe,  Ariz. 
Harpers  Ferry,  Va. 
Hartville,  Wyo. 
Huntington,  W.  Va. 
Jackson,  Cal. 
La  Plata,  Colo. 
Laramie-Sherman,  Wyo. 
Lassen  Peak,  Cal. 
Livingston,  Mont. 
Marysville,  Cal. 
Mount  Stuart,  Wash. 
Nampa,  Idaho. 
Nepesta,  Colo, 


Oelrichs,  S.  D. 
Patoka,  Ind. 
Pawpaw— Hancock,  Md. 
Pikes  Peak,  Colo. 
Port  Orford,  Ore. 
Placerville,  Cal. 
Pueblo,  Colo. 
Pyramid  Peak,  Cal. 
Redding,  Cal. 
Rome,  Ga. 
Sacramento,  Cal. 
Scotts  Bluff,  Neb. 
Silver  City,  Idaho. 
Silverton,  Colo. 
Smartsville,  Cal. 
Sonora,  Cal. 
Spanish  Peaks,  .Colo. 
TeUuride,  Colo. 
Tenmile  District,  Colo 
Three  Forks,  Mont. 
Tintic,  Utah. 
Truckee,  Cal. 
Uvalde,  Texas. 
Yellowstone,  Wyo. 


EXERCISE  XIII 

PLEISTOCENE  AND  RECENT 

I.  FOLIOS  TO  BE  STUDIED 

A.  Folios  for  More  Elementary  and  Briefer  Courses 
Aberdeen-Redfield,  S.  D.     Lancaster-Mineral  Point, 
Ann  Arbor,  Mich.  Wis. 

Beaver,  Pa.  Masontown-Uniontown,  Pa. 

Brownsville-Connellsville,  New  York  City,  N.  Y. 

Pa.  Passaic,  N.  J. 

Burgettstown-Carnegie,       Patoka,  Ind. 

Pa.  Rockland,  Me. 

Chicago,  111.  Sewickley,  Pa. 

Cloud  Peak-Fort  McKin-  Tacoma,  Wash. 

ney,  Wyo.  Warren,  Pa. 

Colfax,  Cal.  Watkins  Glen-Catatonk, 

Gaines,  Pa.  N.  Y. 

B.  Additional  Folios  for  More  Advanced  Courses 
Bismarck,  N.  D.  Jamestown-Tower,  N.  D. 
Casselton-Fargo,  N.  D.       Latrobe,  Pa. 
Choptank,  Md.                      Norfolk,  Va. 
Claysville,  Pa.                       Olivet,  S.  D. 

Dover,  Del.  Ouray,  Colo. 

Elders  Ridge,  Pa.  Parker,  S.  D. 

Elk  Point,  S.  D.  Patuxent,  Md. 

Ellensburg,  Wash.  Philadelphia,  Pa. 

Engineer  Mountain,  Colo.  St.  Marys,  Md. 
Foxburg-Clarion,  Pa.  Trenton,  N.  J. 

Flanklin  Furnace,  N.  J.       Waynesburg,  Pa. 
Fredericksburg,  Va. 

69 


70        STRUCTURAL  AND  HISTORICAL  GEOLOGY 

H.  DIRECTIONS 

Elementary  Courses. — Study  only  the  folios  of  Group  A. 
Prepare  answers  to  all  questions  not  marked  **,  and  answer 
in  writing  questions  marked  *. 

Advanced  Courses. — Study  all  the  folios  of  A  and  B  above, 
using  those  of  Group  B  especially  for  answering  the  General 
Questions.  Answer  in  writing  questions  marked  *  and  **. 

Note. — In  this  exercise,  Surficial  Geology  sheets  should  be 
studied  where  they  are  found  in  the  folios,  and  free  use 
should  be  made  of  the  folio  texts. 

HI.  QUESTIONS 

Rockland  Folio: 

*1.  What  was  the  chief  event  of  the  Pleistocene  period  in 
this  district,  as  shown  by  the  character  of  the  Pleistocene 
formations  ? 

**2.  What  is  the  maximum  relative  change  of  level  recorded 
in  the  Rockland  quadrangle,  since  glaciation?  (See  the 
distribution  of  Qmc  of  the  Surficial  Geology  map,  and 
"Marine  Clay,"  p.  5.) 

New  York  City  Folio: 

1.  Note  the  topographic  expression  of  the  Ptm  belt  on  the 
Brooklyn  and  Staten  Island  sheets  (Surficial  Geology 
sheets). 

*2.  The  origi  n  of  the  plain  of  Psd  across  these  quadrangles  ? 
Note  its  influence  on  the  location  of  suburban  towns. 

3.  Outline  the  Pleistocene  history  of  this  region. 

Passaic  Folio: 

1.  Study  the  Surficial  Geology  Sheet  for  various  phases  of 
glacial  deposits. 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        71 

*2.  Account  for  the  southward  loop  of  Qtm  east  of  the 
Watchung  Mountains. 

3.  a)  Note  the  distribution  of  Qk  and  Qdr. 
**b)  How  would  you  distinguish  between  Qk  and  Qdr 
in  the  field  ? 

Franklin  Furnace  Folio: 

**1.  Work  out  a  plausible  hypothesis  for  the  origin  of  the 
areas  of  Qd  north  of  Franklin  Junction  (central  rectangle), 
east  of  Deckertown  (north  central  rectangle),  and  near 
Northup  (west  central  rectangle). 

**2.  Note  the  large  kames,  Qk,  in  the  vicinity  of  Hamburg 
(east  central  rectangle),  and  the  lesser  kames  in  association 
with  the  other  deltas,  Qd.  Has  the  association  of  kames 
and  deltas  any  significance  ? 

**3.  Draw  diagrams  which  shall  illustrate  the  conditions 
under  which  the  kame  terraces  of  the  quadrangle  originated. 
**4.  Work  out  a  hypothesis  for  the  peculiar  area  of  Qk  at 
Ogdensburg.  Note  that  it  extends  directly  across  a  wide 
valley,  except  for  the  narrow  gap  through  which  the  Wallkill 
River  runs.  This  gap  is  probably  post-glacial. 

Watkins  Glen-Catatonk  Folio: 

1.  Note  the  distribution  of  Qtd.  Were  the  present 
drainage  lines  of  this  area  developed  before,  during,  or  after, 
the  Wisconsin  glacial  epoch  ? 

*2.  Explain  the  origin  of  the  broad  flat  north  of  Elmira  and 
west  of  Horseheads,  Watkins  Glen  quadrangle. 

3.  a)  Note  the  location  of  eskers  within  and  along  stream 
valleys. 

**b)  What  is  the  significance  of  this  relation  in  con- 
nection with  the  origin  of  eskers  ? 


72        STRUCTURAL  AND  HISTORICAL  GEOLOGY 

Fredericksburg  and  Norfolk  Folios: 

*1.  Interpret  the  Columbia  formation,  as  shown  in  these 
folios. 

Ann  Arbor  Folio: 

**1.  Correlate  the  several  beach  ridges  with  the  successive 
lines  of  drainage  from  this  area  during  the  retreat  of  the 
Wisconsin  ice  sheet.  (See  pages  10  and  11  of  the  text.) 

2.  Note  the  location  of  this  quadrangle  with  reference  to 
the  Saginaw  and  Huron-Erie  ice  lobes  (Fig.  5,  p.  4  of  the 
text). 

*3.  Explain  the  abrupt  constriction  of  the  Huron  valley 
at  Dexter,  nine  miles  northeast  of  Ann  Arbor. 

4.  The  origin  of  the  band  of  Qgo  and  Qlc  stretching  from 
Ann  Arbor  southwest  through  Clinton  and  Tecumseh. 

*5.  Contrast  the  topography  of  this  area  with  that  of  the 
Patoka  and  Gaines  quadrangles.     Explain  the  differences. 

Patoka  Folio: 

*1.  After  a  careful  study  of  the  legend,  outline  the  Quater- 
nary history  of  this  region. 

2.  Does  the  formation  Tr  about  two  miles  north  of 
Princeton,  have  any  significance  with  reference  to  the  time 
limits  within  which  the  present  relief  was  developed  ? 

Chicago  Folio: 

**1.  After  a  careful  study  of  the  topography,  distribution, 
and  character  of  the  Pleistocene  rocks,  and  the  elevation 
and  distribution  of  the  shorelines,  outline  the  glacial  and 
post-glacial  history  of  the  region. 

2.  Account  for  the  bowlder  deposits  in  the  northern  part 
of  the  Desplaines  quadrangle. 
*3.   History    (date   of   origin,    source    of   sand,    etc.)    of 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        73 

the  dunes   east   and  south  of  Evergreen  Park,    Calumet 
quadrangle  ? 

4.  There  are  several  outcrops  of  rock  in  the  area  covered 
by  this  folio.  From  this,  and  from  the  further  fact  that  the 
drift  is  more  than  100  feet  deep  at  some  points  near  the 
outcrops,  what  inference  can  be  drawn  as  to  the  topography 
of  the  Niagara  limestone  ? 

Milwaukee  Folio: 

1.  Note   the   various   kinds   of  glacial   deposits   in   the 
region. 

2.  What  effect  did  the  ice  have  on  the  drainage  ? 

*3.  In  what  ways  might  the  outcrop  of  Dm  along  Milwau- 
kee River  1  mile  north  of  Milwaukee  be  explained  ?  Which 
is  the  most  probable  explanation  ? 

4.  The  meaning  of  the  appearance  of  Dm  at  the  quarry 
on  the  shore  of  Whitefish  Bay? 

**5.  How  could  the  character  of  the  surface  of  the  Paleozoic 
rocks  in  this  region  be  ascertained  ? 

Lancaster-Mineral  Point  Folio: 

1.  a)  What  part  of  this  region  was  glaciated  during  the 
Pleistocene  period  ? 

b)  During  which  glacial  epoch  was  it  glaciated  ? 
*2.  Account  for  the  areal  distribution  of  Ql  (Lancaster 
quadrangle). 

**3.  Work  out  an  explanation  for  the  formation  of  the 
terraces,  Qt,  in  the  valleys  tributary  to  the  Mississippi. 

Jamestown-Tower  and  Casselton-Fargo  Folios: 

1.  What  was  the  origin  of  the  Qla  formation?     Of  the 

Qd  formation  ? 

**2.  Correlate  the  terrace  deposits  along  Sheyenne  River 


74       STRUCTURAL  AND  HISTORICAL  GEOLOGY 

(Casselton    quadrangle)    with    successive    stages    of  Lake 
Agassiz. 

3.  Note  the  section  on  p.  3,  Casselton-Fargo  folio. 
**4.  Work  out  the  probable  history  of  the  bowlders  in  the 
Qb  formation. 

5.  The  source  of  the  sand  in  the  Qds  formation  ? 

Aberdeen-Red  field  Folio: 

1.  Study  the  four  Areal  Geology  sheets  in  the  folio,  for 
the  general  results  of  glaciation  in  the  region. 

2.  Which  of  the  Pleistocene  ice  sheets  (early,  late)  affected 
the  region  ? 

3.  Note  the  topographic  expression  of  the  Qam  and  Qld 
formations. 

4.  What  is  the  meaning  of  the  Qod  formation  ? 

Cloud  Peak-Fort  McKinney  Folio: 

1.  Note  the  character  and  distribution  of  the  Quaternary 
deposits. 

2.  Note  the  distribution  of.  Ql,  Cloud  Peak  Sheet,  and 
explain  its  origin. 

3.  Give  plausible  hypotheses  to  explain  the  origin  of  Qt. 
**4.  a)  What  field  evidence  would  you  use  to  distinguish 
earlier  glacial  drift  from  later  glacial  drift  ? 

b)  How  would  you  establish  the  age  of  Qvt,  Cloud 
Peak  Sheet? 

Ouray  and  Engineer  Mountain  Folios: 

**1.  Discuss  the  map  evidence  for  two  periods  of  glaciation 
in  this  region. 

2.  Give  some  idea  of  the  time  that  elapsed  between  the 
two  epochs  of  glaciation. 


STRUCTURAL  AND  HISTORICAL  GEOLOGY        75 

Colfax  Folio: 

1.  Estimate  the  amount  of  post-glacial  cutting  by  the 
Yuba  River  near  Emigrant  Gap,  northeast  corner  of  central 
rectangle. 

Ellensburg  Folio: 
**1.  What  is  the  origin  of  the  Cowiche  gravels? 

Tacoma  Folio: 

*1.  State  plausible  hypotheses  for  the  origin  of  the  broad 
depressions  occupied  by  Puget  Sound  and  tributary  valleys. 

General  Questions 

•**1.  How  many  epochs  of  glaciation  are  represented  in 
Pennsylvania,  as  shown  by  the  folios?  Ditto  in  South 
Dakota  ?  Ditto  in  Colorado  ? 

**2.  Work  out  an  hypothesis  which  satisfactorily  explains 
the  constitution  and  distribution  of  the  Carmichael  forma- 
tion, as  shown  in  the  western  Pennsylvania  folios. 
**3.  Outline  the  post-Miocene  history  of  the  Chesapeake 
and  Delaware  Bay  region,  as  shown  by  the  constitution, 
the  stratigraphic  relations,  and  the  topographic  distribution 
of  the  post-Miocene  deposits.  Both  deposits  and  changes 
of  level  are  to  be  considered.  See  especially  the  Trenton, 
Philadelphia,  Dover,  Patuxent,  and  St.  Marys  folios. 

*4.  Locate  three  clearly  defined  cases  of  drainage  changes 
due  to  sheet  glaciation. 

**5.  What,  if  any,  products  of  economic  value  do  the 
Pleistocene  glacial  deposits  contain  ?  Non-glacial  ? 

6.  How  would  you  determine  in  the  field  whether  a 
mountain  valley  had  been  glaciated  ? 

*7.  Make  a  list  of  non-glacial  or  only  indirectly  glacial 
Pleistocene  deposits  shown  on  the  folios. 


76        STRUCTURAL  AND  HISTORICAL  GEOLOGY 


*8.  What  deposits  of  the  Recent  period  are  shown  on  the 
maps? 

Many  of  the  folios  of  the  United  States  Geological  Survey 
show  deposits  of  Quaternary  (Pleistocene  and  Recent)  age,  but  a 
few  of  the  more  valuable  ones  for  more  extended  work  with  these 
systems  are  listed  below: 


Absaroka,  Wyo. 

Alexandria,  S.  D. 

Amity,  Pa. 

Anthracite-Crested  Butte,  Colo. 

Bald  Mountain-Dayton,  Wyo. 

Bidwell  Bar,  Cal. 

Big  Trees,  Cal. 

Danville,  111. 

De  Smet,  S.  D. 

Ditney,  Ind. 

Downieville,  Cal. 

Fort  Benton,  Mont. 

Holyoke,  Mass. 

Huron,  S.  D. 

Kittanning,  Pa. 

Lassen  Peak,  Cal. 

Little  Belt  Mountains,  Mont. 


Livingston,  Mont. 
Mitchell,  S.  D. 
Needle  Mountains,  Colo. 
Nomini,  Md. 
Placerville,  Cal. 
Pyramid  Peak,  Cal. 
Rogersville,  Pa. 
Rural  Valley,  Pa. 
Silverton,  Colo. 
Snoqualmie,  Wash. 
Telluride,  Colo. 
Three  Forks,  Mont. 
Tintic,  Utah. 
Truckee,  Cal. 
Washington,  D.  C. 
Yellowstone,  Wyo. 


Chamberlin  and  Salisbury's  Geology 

By  THOMAS  C.  CHAMBERLIN  AND  ROLLIN  D.  SALISBURY, 
Professors  in  the  University  of  Chicago.  (American  Science  Se- 
ries, Advanced  Course.)  3  Volumes  8vo. 

Volume    I.    Processes    and    Their    Results.      xIx-j-654    pp.    $4.00 
Volumes    II    and    III.      Earth    History.      xxvi-|-692-j-xi-j-624    pp. 
Vols.  II  and  III  not  Sold  separately.    $8.00. 

Chas.  D.  Walcott,  Director  of  U.  S.  Geological  Survey:—!  am 

impressed  with  the  admirable  plan  of  the  work  and  with  the  thorough 
manner  in  which  geological  principles  and  processes  and  their  results 
have  been  presented.  The  text  is  written  in  an  entertaining  style, 
and  is  supplemented  by  admirable  illustrations,  so  that  the  student 
cannot  fail  to  obtain  a  clear  idea  of  the  nature  and  work  of  geological 
agencies,  of  the  present  status  of  the  science,  and  of  the  spirit  which 
actuates  the  working  geologist. 

Israel  C.  Russell,  Professor  in  the  University  of  Michigan: — 
The  work  is  certainly  monumental,  and,  like  Lyell's  Principles  of 
Geology,  will  in  the  future,  I  am  confident,  be  recognized  as  marking 
the  beginning  of  a  new  period  in  the  development  of  the  science  of 
the  earth. 

R.  S.  Woodward,   Director  of  the  Carnegie  Institution: — It  is 

admirable  for  its  science,  admirable  for  its  literary  perfection,  and 
admirable  for  its  unequalled  illustrations. 


College  Geology 


By  T.   C.  CHAMBERLIN  AND  R.  D.   SALISBURY.    (American 
Science  Series.)  xvi  4-978  pp.    8vo.    $3.50. 

A  one-volume  text-book  on  the  lines  of  the  authors'  widely 
known  three-volume  work.  It  supplies  ample  material  for  the  av- 
erage college  course  in  geology. 

T.  C.  Hopkins,  Professor  in  Syracuse  University:  —  I  find  it  so 
far  in  advance  of  the  other  text-books  I  have  seen  that  I  decided  to 
use  it  in  my  class. 

A.  H.  Purdue,  Professor  in  Me    University  of  Arkansas:—  It 

probably   will   be   the   standard   college   text-book   in    Geology    for 
several  years  to  come. 

E.  N.  Lowe,  Director  of  Geological  Survey,  Jackson,  Miss..-  —  It 

is  an  unrivaled  text-book  for  a  brief  course  in  general  geology. 


TTTWRV    TJOT   T    &    TO  34  West  33*  Street,  New  York 

Xl  Hi  IN  XV  I     ±1UJL«JL     <X    \^*J.  378  Wabasn  Avenue,      Chicago 


Salisbury's  Physiography.  Advanced  Course 

By  ROLLIN  D.  SALISBURY,  Professor  in  the  University  of  Chi- 
cago. (American  Science  Series,  Advanced  Course.)  xx-j~77O 
pp.  8vo.  $3.50. 

While  planned  for  courses  in  colleges  and  normal  schools,  it 
presupposes  no  previous  study  of  physical  geography. 

W.  M.  Davis,  Harvard  University: — It  is  an  important  addition 
to  college  literature,  the  first  book  of  college  grade  on  physiography. 
The  illustrations  are  for  the  most  part  remarkably  successful  and 
appropriate. 


Salisbury's  Physiography  for  High  Schools 

By  ROLLIN  D.  SALISBURY,  Professor  in  the  University  of  Chi- 
cago. (American  Science  Series,  Briefer  Course.)  viii-}-53i 
pp.  Large  I2mo.  $1.50. 

This   is   intended  to   cover  the   work   in  physical   geography   as 
given  in  the  first  or  second  year  of  the  high  school. 

W.  H.  Hawkes,  Ann  Arbor  (Mich.}  High  School:— I  am  of  the 

opinion,  after  careful  examination  of  the  leading  Physiographies 
on  the  market,  that  Salisbury's  Briefer  Course  of  Physiography  is 
in  the  lead,  in  the  method  of  treatment  of  the  subject  of  Earth 
Science,  its  clearness  of  presentation  of  detail,  and  especially  in  the 
ways  in  which  the  subject  matter  is  discussed  in  illustrative  dia- 
grams, 

Salisbury's  Elementary  Physiography 

By  ROLLIN  D.  SALISBURY,  Professor  m  the  University  of 
Chicago.  (American  Science  Series,  Elementary  Course.) 
xi  +  359  pp.  47  plates.  Large  i2mo.  $1.30. 

This  is  particularly  well  adapted  to  first  year  pupils  and  short  enough 
for  a  half-year  course  if  need  be. 

C.  L.  Walton,  Lake  View  High  School,  Chicago: — "It  would  seem 
that  nothing  further  could  be  done  in  the  way  of  perfecting  a  text-book  in 
elementary  physiography.  As  we  are  to  have  but  five  months  of  this  study 
hereafter,  I  think  no  other  book  is  so  well  adapted  to  our  needs  as  this  one." 

HKN"RV    TTOT  T    XT    PO  3*  West  33d  Street,  New  York 

XlXlilN  XV I     XHJl_j  1     <X    VLJ.  37s  wabash  Avenue       Chicago 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN  INITIAL  FINE  OF  25  CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


SEP 


LD  21-20m-5, '39  (9269s) 


